OA17011A

OA17011A - Wear resistant material and system and method of creating a wear resistant material.

Info

Publication number: OA17011A
Application number: OA1201400338
Authority: OA
Inventors: Srinivasarao Boddapati
Original assignee: Esco Corporation
Priority date: 2012-01-31
Filing date: 2013-01-29
Publication date: 2016-02-26

Abstract

A system and method of forming a wear resistant composite material includes placing a porous wear resistant filler material in a mold cavity and infiltrating the filler material with a matrix material by heating to a temperature sufficient to melt the matrix material, then cooling the assembly to form a wear resistant composite material. The system and method can be used to form the wear resistant composite material on the surface of a substrate, such as a part for excavating equipment or other mechanical part. One suitable matrix material may be any of a variety of ductile iron alloys.

Description

WEAR RESISTANT MATERIAL AND SYSTEM AND METHOD OF CREATING A WEAR RESISTANT MATERIAL

DESCRIPTION

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The présent application claims priority to and the benefit of U.S. Provisional Application No. 61/593,091, filed January 31,2012, which application is incorporated by reference herein in its entirety and made part hereof.

TECHNICAL FŒLD [0002] The présent invention generaliy relates to Systems and methods for creating a wear résistant material, and more specifically, to Systems and methods that utilize infiltration techniques to form the wear résistant material and connect the material to a substrate by brazing, as well as a product of the system and method.

BACKGROUND [0003] Various types of excavaling equipment hâve points, edges, surfaces, and other parts that are subjected to repeated impacts and stresses, which may resuit in wearing or fracture of such parts. Accordingly, materials having high hardness and wear résistance coupled with good toughness are désirable for such applications. Materials with high hardness and wear résistance may be useful in other applications as well, including applications where similar challenges are faced.

[0004] One common technique for producing wear résistant parts is casting the part by pouring a moltcn métal (e.g. cost Iron) around a hard, wear résistant material placed in the mold to attach lhe wear résistant material lo the casi métal part and create a wear résistant composite. A major drawback of this method is that lhe substrate onto which 25 lhe wear résistant material is attached by this method is limited to the materials that are suitable for casting. Additîonally, the wear résistant material is generaliy limited to volume fraction ranges of 5-50% and iimited to particles greater than 50pm, and the parts are generaliy limited to thicknesses less than 6.25 mm (0.250 Inch). Further, this method requires superheating the molten alloy lo about 200°C to 400°C, which leads to 30 significanl dissolution of cart) i de particles and thereby dégradés lhe properties of the

résultant composite. Still further, because such casting is done in air, there is a possibility for oxidation of both hard particles and the matrix métal, and oxides may become entrapped in the composite and dégradé the wear and mechanical performance.

[0005] Another common technique for producing wear résistant parts is the infiltration of nickel based alloys, copper based alloys, and/or cast iron into a porous mass of both pure tungsten carbide and cemented carbide particles. However, nickel and copper based alloys are expensive, and cast iron does not hâve loughness that is satisfactory for ail applications. Ductile iron représenta a much more economical material that is castable and has good fracture toughness. However, the conditions employed for these techniques are not suitable for ductile iron infiltration. In addition, the infiltration températures involved in these techniques are so high that significant dégradation of hard particles takes place. In the case of infiltration of cast iron into spherical cast carbides using these techniques, the original carbide particles may complctcly disintegrate. As a resuit of metallurgicaJ interaction between the molten binder mêlais with hard carbide particles, the particle size for such techniques must typicaliy be kept above 1,14mm (0.045 inch). so that even after reaction there is still comparatively significant fraction of hard particle left to provide wear résistance.

[0006] Accordingly, while certain existing products and methods provide a number of advantageous features, they nevertheless hâve certain limitations. The présent invention seeks to overcome certain of these limitations and other drawbacks of the prior art, and to provide new features not heretofore available.

BREF SUMMARY [0007] The following présents a general summary of aspects of the invention in order to provide a basic understanding of the invention. This summary is not an extensive 25 overview oflhe invention. It is not intended to identify keyorcritical éléments ofthe invention or to delineate the scope of lhe invention. The following summary merely présents some concepts of the invention in a general form as a préludé to the more detailed description provided below.

[0008] Aspects of the présent invention relate to a meihod for use in forming a wear 30 résistant composite coating on a substrate. A mold is positioned proximate a surface of

the substrate, such that the surface is tn communication with a cavity of the mold, and a porous wear résistant material is placed within the cavity, in close proximity to the surface. A metallic matrix material is then placed in communication with lhe cavily, and the mold and the matrix material are heated lo a température above a melting point of the 5 matrix material. The température is held above the melting point for a time sufficient for the matrix material to infiltrate the wear résistant material in molten form and contact the surface of the substrate. Thereafler, the mold and the matrix material are cooled to solîdify the matrix material and form a wear résistant composite coating that includes the wear résistant material embedded within the matrix material on the surface of the substrate. The matrix material may be ductile iron in one embodiment. and the ductile iron may hâve a composition that includes, in weight percent, approximately 3.0-4.0% carbon, approximately 1.8-2.8% silicon, approximately 0.1-1.0% manganèse, approximately 0.01-0.03% sulfur, and approximately 0.01-0.1% phosphorous, with the balance being iron and incidental eiements and impurilies. It is understood that other eiements and additions may be included in the ductile iron, such as nickel (up to 37 wt.%), chromïum (up to 5.5 wt.%), and/or silicon (up to 5.5 wt.%).

[0009] According to one aspect, lhe wear résistant material may include one or more materials selected from the group consisting of: carbides, nitrides, bondes, si licides, intermetallic compounds oftransition metals, and combinations thereof. Examples of carbides thaï may be used include: WC, TiC, SiC, CrjCi, VC, ZrC, NbC, TaC, (W,Ti)C, BuC, and Mo^C, and combinations thereof. Examples of nitrides that may be used include: TiN, BN, SijN₄. ZrN, VN, TaN, NbN, HfN, CrN. MoN, and WN, and combinations thereof. Examples of borides that may be used include: titanium bonde, chromium bonde, tungsten bonde, nickel bonde, zirconium boride. hafnium boride, tantalum boride. niobium boride, vanadium boride. molybdenum boride. silicon boride, alumlnum boride. and other borides of transition metals. and combinations thereof. Examples of silicides thaï may be usai include silicides of transition metals. The wear résistant material may further hâve a wetting compatible coating.

[0010] According to another aspect, lhe composite coating may be formed on a plurality of surfaces of the substrate, or may be formed on only a portion of the surface of lhe substrate.

[0011] According to a further aspect, the porous wear résistant material may be in the form of a loose particulate material or in the form of a porous preform formed of a particulate material bonded together to form lhe porous preform. The particulate material in the preform may be bonded together in several different ways, such as by sinteringorby a polymer material. Ifa polymer material is used for bonding, the material may be selected so that the brazïng température is sufficient to remove the polymer material from lhe particulate material during heating.

[0012] According lo yet another aspect, lhe mold may be or include a sheet métal shell connected to the substrate to defîne the cavity. The shell may hâve an opening lo 10 an exterior of the shell, and lhe porous wear résistant material may be piaced within the cavity by insertion through lhe opening. Such a shell may hâve a watt thickness significantly lower thon lhe thickness of lhe subslrate, and may be welded to the outer surface of lhe subslrate.

[0013] According to a still further aspect, lhe heating is performed within a fumace 15 chamber, and lhe chamber may beevacualed (e.g. 0.0001 or 0.001 Torrlo 0.010 Τοπ, or even lower pressure) prior lo the température reaching the melting point of the matrix material. An inert gas may be introduced into the chamber after the matrix material has melted. Altemately, the melting may be performed in lhe presence of an inert gas, such as by introducing argon gas into lhe chamber before the matrix material has melted. ln 20 this embodiment, the mold has a permeable portion in contact with the porous wear résistant material lo permit residual gas to escape from the permeable portion during infiltration.

[0014] According lo an additional aspect, the matrix material may be positioned at least partially laterally or horizontally to lhe wear résistant material, and the method may 25 further include placing a displacement medium (e.g. a flowable medium such as ceramîc beads) adjacent to the matrix material and opposite the wear résistant material. The displacemenl medium supports the molten matrix material and displaces the molten matrix material as lhe molten matrix material infiltrâtes lhe wear résistant material. A barrier may further be piaced between the displacement medium and the matrix material, 30 to resist perméation ofthe molten matrix material into lhe displacement medium. One example of latéral infiltration is when the substrate is a tubular structure, such that the

molten matrix material infiltrâtes latéral!y outward to form lhe composite coating on the inner surface of the tubuiar structure. In this configuration, the displacement medium is placed at a center of the tubuiar structure and displaces outwardly us the molten matrix material Infiltrâtes the wear résistant material.

[0015] Additional aspects of the Invention relate to a system for use in forming a wear résistant composite coating on a surface of a substrate. The System may include a mold positioned in proximily to the surface of the substrate, such that the surface is in communication with the mold cavity, a porous wear résistant material within the cavity. In close proximily to the surface, and a metallic matrix material in communication with 10 the cavity. The system may be usable in connection with a method according to the aspects described above, such as heating the mold and the matrix material to a température above a melting point of the matrix material and holding the température for a time sufficient for the matrix material to înfîltrate the wear résistant material in molten form and contact the surface of the substrate, and then cooling the mold and the matrix 15 material to solidify the matrix material and form a wear résistant composite coating on the surface of the substrate. As described above, the matrix material may be ductile iron.

[0016] According to one aspect, the wear résistant material may include one or more materials selected from the group consisting of: carbides. nitrides, bondes, silicides, inlcrmetallic compounds of transition metals, and combinations thereof, including the 20 materials described above.

[0017] According to another aspect, lhe porous wear résistant material may be in the form of a loose particulate material or in lhe form of a porous preform formed of a particulate material bonded together to form the porous preform, as described above.

[0018] Further aspects of the invention relate to an article of manufacture, which may be manufactured according to a Systems and/or a method according to the aspects described above or by other Systems and/or methods. The article includes a metallic substrate having a surface with a wear résistant composite coating bonded to the surface. The wear résistant composite coating includes a wear résistant particulate material, as well as a metallic matrix material bonding together the wear résistant particulate material. The coating may be a continuous coating. The matrix material is further

bonded to lhe surface of the substrate to bond the wear résistant composite coating to the substrate. The metaltic matrix material may be ductile iron, which may hâve a composition as described above. The method may be used to make coatings having thicknesses of at least 0.005 inches, and typically greater than 0.040 inches. The method 5 may achieve infiltration distances of up to 6 inches or more, or up to 7.5 inches or more in some embodiments, and may therefore be used to make coatings having a greater thickness than the substrate itseif, such as up to 6 inches or more, up to 7.5 inches or more, or even greater thicknesses in various embodiments.

[0019] According to one aspect, the wear résistant material may include one or more 10 materials selected from the group consisting of: carbides, nitrides, bondes, silicides, intermetallic compounds of transition metals, and combinations thereof, including the examples described above.

[0020] According to another aspect, the substrate has a plurality of protrusions connected to the surface and extending outwardly from the surface. The protrusions arc 15 embedded within the wear résistant composite coating. As one example, the protrusions may be a plurality of rib or plate members symmetrically distributed on the outer surface ofthe substrate.

[0021] According to a further aspect, the article may be a wear member for excavating, mînîng, or other earthmoving equipment, and the substrate may be formed 20 by a working portion of the wear member, such thaï the composite coating overlays the working portion.

[0022] Other features and advantages of the invention will be apparent from the following description taken in conjunction with the attached drawings.

BRIEF DESCRIPTION OFTHE DRAWINGS [0023] To ailow for a more full understanding of the présent invention, it will now be described by way of example, with reference to the accompanying drawings in which:

[0024] FIG. I is α schematic illustration showing an example of vertical infiltration from above to form a wear résistant composite material, according to one embodiment of the présent invention;

[0025] FIG. 2 is a schematic illustration showing an example of vertical infiltration from below to form a wear résistant composite material, according to one embodiment of the présent invention;

[0026] FIG. 3 is a schematic illustration showing an example of horizontal infiltration to form a wear résistant composite material, according to one embodiment of the présent invention;

[0027] FIG. 4 is a schematic illustration showing one embodiment of a system and method of forming a wear résistant composite material on a substrate using vertical infiltration, prior to infiltration, according to aspects of the présent invention;

[0028] FIG. 5 is a schematic illustration showing the substrate having lhe wear résistant composite material formed lhereon using lhe method as shown in FIG. 4, after 15 infiltration, according to aspects of lhe présent invention;

[0029] FIG. 6 is a schematic illustration showing another embodiment of a system and method of forming a wear résistant composite material on a substrate using outward infiltration, prior to infiltration, according to aspects ofthe présent invention;

[0030] FIG. 7 is a schematic illustration showing a cross-section of lhe system as shown in FIG. 6;

[0031] FIG. 8 is a schematic illustration showing another embodiment of a system and method of forming a wear résistant composite material on a substrute using vertical and horizontal infiltration, prior to infiltration, according to aspects of lhe présent invention;

[0032] FIG. 9 is a schematic il lustration showing another embodiment of a System and method of forming a wear résistant composite material on a substrute using vertical and horizontal infiltration, prior to infiltration, according to aspects of the présent invention;

[0033] FIG. 10 is a photomicrograph illustrating an example of spherical cast tungsten carbîde particles in a ductile iron matrix, produced using a method according to the présent invention;

[0034] FIG. 11 is a photomicrograph illustrating an interface between a spherical cast 5 tungsten carbide / ductile iron composite and excess ductile iron remaining after the infiltration process using a method according to the présent invention;

[0035] FIG. 12 is a schematic illustration showing another embodiment of a substrate having the wear résistant composite material formed thereon using an infiltration method, according to aspects of the présent invention;

[0036] FIG. 13 is a schematic Illustration showing an example of a system and method for infiltration of a porous wear résistant material with a braze material In a fumace under vacuum conditions, according to another embodiment of the présent invention;

[0037] FIG. 14 is a schematic Illustration showing on example of a system and method for infiltration of a porous wear résistant material with a braze material in a fumace under vacuum conditions prior to melting of the braze material, according to one embodiment of the présent invention;

[0038] FIG. 15 is a schematic illustration of lhe system and method of FIG. 14, with partial Ar pressure introduced Into the fumace after melting of the braze material;

[0039] FIG. 16 is a schematic illustration showing an example of a system and method for infiltration of a porous wear résistant material with a braze material in a fumace under partial Ar pressure, according to another embodiment of the présent invention;

[0040] FIG. 17 is a perspective view of another embodiment of a substrate configured for use according to aspects of the présent invention, in the form of a point for excavating or mining equipmeni;

[0041] FIG. 18 is a cross-sectional view of the substrate of FIG. 17, having a wear résistant composite material formed on an outer surface thereof;

[0042] FIG. 19 ïs a perspective view of one embodiment of a shell configured for use as a mold for forming a wear résistant composite materia! according to aspects of the présent invention; and [0043] FIG. 20 is a cross-sectional view of the shell of FIG. 19 connected to one embodiment of a substrate in the form of a point for excavating or mining equipment, configured for use in forming a wear résistant composite material according to aspects of the présent invention.

D ETA ILE D DESCRIPTION [0044] While this invention is susceptible of embodiment in many different forms, there are shown în the drawings, and wiii herein be described in detail, preferred embodiments of the invention with the understanding that the présent disclosure is to be considered as an exemplification of the principes of the invention and is not intended to limit the broad aspects of the invention to the embodiments illustrated and described.

[0045] In general, aspects of the invention relate to Systems and methods of forming 15 a wear résistant composite material that include placing a porous wear résistant fil 1er material in a moid cavity and infïltrating the filler material with a matrix material by heating to a température sufficient to melt the matrix material, then cooling the assembly to form a wear résistant composite material. The résultant composite material includes the matrix material intermixed with the filler material and bonded to lhe filler material, 20 where the matrix material bonds lhe composite to the substrate and also may bond together lhe filter material. The system and method can be used to form the wear résistant composite material on the surface of a substrate, such as a part for mining, excavating, or other earthmoving equipment or other mechanical part. It is understood thaï the “surface of a substrate as described herein may include a plurality of different 25 surfaces, and does not imply any spécifie contour to such surface(s) unless explicitly noted. The substrate can be any material with a meltîng point that is suitabie for the infiltration process, for example having a meiling point thaï is higher than the matrix material. Examples ofsuch substrates include cast, wroughl, and powder metallurgyproduced metallic materials, as well as ceramics and ceramic-based materials such as 30 metuliized ceramics. In one embodiment, the subslrate may be carbon steel, alloy steel,

stainless steel, or too! steel. The system and method can altemately be used (o form the wear résistant composite material os a unitary piece.

[0046] In one embodiment, lhe method utilizes ductile iron as the matrix material and produces a dense, hard, and tough composite with excellent wear résistance and toughness. Additionally, ductile iron has a melting point that Is sufficiently low to enable melting without excess heating. AU types/grades of ductile iron may be usable in accordance with the invention, including any ductile iron that is within the scope defined by ASTM standard A536-84 (Reapproved, 2004), which is incorporated by reference herein. In one embodiment, a ductile iron matrix material may hâve a composition, in weight percent, of approximately 3.0-4.0% carbon; approximately 1.8-2.8% silicon; approximately 0.1-1.0% manganèse, approximately 0.01-0.03% sulfur, and approximately 0.01-0.1% phosphorous, with the balance being iron and incidental éléments and impurities. As used herein, the term approximately” désignâtes a variance of +/-10% of lhe nominal values listed (e.g. the endpoints of the composition ranges). In another embodiment, the composition may not include this variance. In a further embodiment, the above composition may include further alloying additions, such as additions of Ni, Cr, and/or Si, to împrove corrosion résistance, wear résistance, and/or high température properties of the matrix material. For example, Ni may be added in amounts of up to 37 wt.%, Cr may be added in amounts of up to 5.5 wt.%, and/or Si may be added in amounts up to about 5 J wt.% in various embodiments. A ductile iron alloy may include still further alloying additions in other embodiments, including alloying additions that may increase performance. Ductile iron alloys with such alloying additions are known as high-alloy ductile irons and generally fall within the scopes of ASTM A439 and A571, which are also incorporated herein by reference. Such alloys may also be utilized in accordance with embodiments of the system and method described herein. In other embodiments, any alloying additions can be utilized to achlevc different properties and/or microstructures, provided that they do not adversely affect the properties or microstnicture in an excessive manner, such as increasing the infiltration température significantly and/or degrading lhe properties of the matrix or the résultant wear résistant material. The method may be utilized to croate a composite with a metallic matrix material other than ductile iron, in an alternate embodiment.

Il [0047] The matrix material may be provided in a variety of forms. For example, in one embodiment, the matrix material may be provided in monolithic form, such as one or more blocks, billets, etc. [n another embodiment, the matrix material may be provided in particulate form, such as powder, fibers, whiskers, etc. ln a further embodiment, the matrix material may be provided in a porous form. The matrix material may be provided ln a combination ofsuch forms in additional embodiments.

[0048] Various hard and wear résistant materials may be used as the filler material in connection with different embodiments, including various carbides, nitrides, borides, and sil icides, as well as other hard and wear résistant materials and mixtures of such materials, Including other types of ceramîc materials. Such materials may be provided in virgîn form and/or with suitable coatings that provide wetting compatibility. For example, where the wear résistant material particles are not wetling-compatible with the matrix material, the wear résistant material particles may be coated with wettingcompatible coatings before they are used for forming lhe composite material by ! 5 infiltration brazing. Carbides that may be used as the filler material include tungsten carbide (WC), TIC, SiC, Cr₃C_:, VC, ZrC, NbC, TuC, (W.Ti)C, B₄C, and Mo₃C, and other carbides. ln one embodiment, spherical cast WC, crushed cast WC, and/or cemented WC is used as lhe filler material. Nitrides lhat may be used as the filler material include TiN, BN, Si₃N₄, ZrN, VN, TaN, NbN, HfN, CrN, MoN, WN, and other 20 nitrides. Borides that may be used as the filler material include borides of transition metals such as titanium boride, chromium bonde, tungsten bonde, nickel bonde, zirconium bonde, hafnium boride, tantalum boride, niobium boride, vanadium boride, molybdenum boride, s'il icon boride, and aluminum boride, as well as other borides. Silicides that may be used as the filler material include silicides of transition metals.

Other materials lhat may be used as filler materials include intermetallic compounds of transition metals. tn one embodiment, the filler material may be selected based on the material having limited solubility in the molten braze material, ln order lo limit or prevent dissolution of the filler material in the braze material. As used herein, the terms matrix material” and “filler material” should not be considered to imply lhat the matrix 30 material or the fii 1er material forms any spécifie proportion of the composite material.

For exaniple, the matrix material need not form a majority or a plurality of the composite

material, and the Ciller material may form a majority or a plurality of the composite material in some embodiments.

[0049] The porous fiiler material may be provided in one or more different forms. In one embodiment, the porous fiiler material may be in the form of a loose particulate material, such as powder, fibers, whiskers, etc. The method may utilité a wide range of particie sites in various embodiments, including particie sites less than 50gm or particie sites less than 1mm. In one embodiment, the particulate fiiler material may hâve a particie site that is greater than O.lpm. In another embodiment, the particulate fiiler material may hâve a particie site that is greater than 0.1 pm and up to 5mm. In a further embodiment, the particulate fiiler material may hâve an average particie site of approximately 500pm. In one embodiment, the fiiler material may be provided in multiple particie sites, such as a combination of coarse and fine particles, which combination can be used to achieve greater density and/or volume fraction of the fiiler material. At any given volume fraction of fiiler material, such use of fine particles generally leads to finer pore sites and can increase the yield strength of the matrix material that fi Ils these pores, thereby increasing the overall wear résistance of the material. When the particulate material is placed in a mold cavity, the spaces between the particles form a porous structure that may be infiItrated by the matrix material. In another embodiment, the porous fi lier material may be in the form of a porous preform.

The porosity of the porous preform can range from 5% to 95% in one embodiment. For example, the porous preform may include a particulate material that is bonded together by a binder material, such as a polymer binder. A preform may be attached to the substrate material, such as by an adhesive that will volatilize during the infiltration process. Upon infiltration, the molten matrix material has sufficient température to remove the binder material (such as by melting, volatilïzatîon, etc.) so that the matrix material can fill the pores left by the removal of the binder in addition to the pores between the particles. As another example, the porous preform may include a particulate material that is bonded together by sintering so that pores exist between the particles. In one embodiment, a pre-sintered preform may hâve a pore size that is on the order of the particie size, since the part may be sintered slightly to achieve neck growth between particles and provide some mechanical handling strength. Other porous materials may be used as well, such as woven fiber mats or fabrics. In a further embodiment, the

porous fi lier material may be provided in a combination of different forms. For example, in one embodiment, the fi lier material may include one or more pre forms forming a portion of the fil 1er material, with other portions being formed by n particulate material (e.g. loose powder, fibers, whiskers, etc.) and/or woven fiber mats or fabrics.

[0050] The brazing operation by infiltration of the fi lier material by the matrix material may generally be accomplished by heating the matrix material to above its melting point while it is in contact or otherwise in communication with the fi lier material, to allow the molten matrix material to contact the filler material and infiltrate the porous filler material. The fîller material is generally placed in contact or otherwise 10 in communication with the substrate during infiltration, in order for the matrix material to contact the substrate material during infiltration to connect the résultant composite material to the substrate. Various molds may be utilized in connection with infiltration, as described below. FIGS. 1-3 illustrate various infiltration configurations according to various embodiments, each schematically illustrating a molten matrix material 16 infiltraling a filler material 15 in a cavity 11 of a mold 12. FIG. I illustrâtes downward vertical infiltration, in which gravity assists the infiltration. However, because the infiltration is mainly driven by capillary action, horizontal infiltration, upward vertical infiltration, outward / radial infiltration, and other infiltration configurations which may not utilize gravity or may work against gravity. FIG. 2 illustrâtes an example of upward 20 vertical infiltration, and FIG. 3 illustrâtes on example of horizontal infiltration. FIGS.

6-7, discussed in greater detail below, illustrate an example of outward or radial infiltration, which may be considered another example of horizontal infiltration. In any non-downward infiltration embodiments, a technique may be utilized to dîsplacc molten matrix material 16 that has infiltrated the filler material 15, in order to kcep the molten 25 matrix material 16 in contact with the filler material 15 until infiltration is complété. For example, the mold 12 may be moved during infiltration to keep the matrix material 16. the filler material 15, and the substrate in proper contact / communication. As another example, a ram or other pressure mechanism may be used to ensure that the matrix material 15 is always in contact with the filler material during infiltration. In a further 30 example, a movable material such os ceramic beads, may be used to displace the infiltrated matrix material, as described below and shown in FIGS. 6-9.

[0051] In one embodiment, the matrix or braze material is superheated 25°C to 75°C greater than the melting point, which is significantly lower than the superheating typically required for casting. In onc example embodiment, where a ductile iron material is used as the matrix material, the infiltration can be conducted at a température range of 5 2150’F to 2275’F, or a température of 2I75’F in another embodiment The holding time period for the infiltration may be from I to 60 minutes in one embodiment, with greater infiltration lengths generally utilizing longer infiltration times. The infiltration may be conducted in an inert atmosphère in one embodiment, such as an argon (Ar) atmosphère, which can avoid volatilizalion-induced molten métal splatter at températures above the 10 melting point. In one embodiment, the argon pressure during infiltration may be approximately 6.5 x 10^s atm to 4 x 1 θ’* atm. Various atmosphères that may be used for infiltration are discussed in greater detail below and illustrated in FIGS. 13-16. Afier infiltration, the part may be cooled, for example, cooling to 1700°F over about 20-30 minutes and then cooling more slowly to room température in one embodiment.

Depending on the nature of the materials involved, particularly the substrate material, post processing such os machining and/or heat treatment may be performed. For example, depending on the identily of the substrate, heat treatments such as normalizing, harde ni n g followed by tempering, or martempering followed by tempering may be performed according to known techniques, [t is understood that some substrates would 20 not benefit from some (or any) heat treatments. Machining may or may not be desired, based on the intended application of the résultant part [0052] The infiltration of the filler material as described above is mainly driven by capillary action, i.e. capillary pressure acting on the infiltration front. The pressure differential ai the infiltration front dépends on many factors, including surface tension of 25 the molten matrix material, contact angle of the molten matrix material with respect to the filler material, géométrie characteristics of the filler material (e.g. porosity, tortuosîty, variation in pore size and shape, and its effect on the apparent contact angle of the molten material), and the pressure ofany residual gas within the filler material. The freedom to control many of these factors may be limited within a spécifie matrix/filler 30 system. Residual gas pressure can bc at least partially controlled, and minimization of residual gas pressure withtn the filler material can maximize the pressure differential and the driving force for capillary action. This, in tum, can maximize the potential distance

that the matrix material can Infiltrate the fïller material. In at least some configurations, the use of fïller material in the form of a preform or preforms may maximizc the infiltration distance as compared to other forms of fïller material.

[0053] FIGS. 13-16 illustrate Systems or assemblies for forming a wear résistant composite material, where different atmosphères are used during the brazïng operation to control and/or minimize the residual gas pressure in the fïller material 15. In these embodiments, the infiltration is performed in a fumace 30 with a chamber 31 holding the mold 12, the matrix material 16, and the fïller material 15. where the atmosphère inside lhe chamber 31 can be controlled. It is understood that lhe assembly may further Include 10 a substrate (not shown) that is in communication with lhe mold 12 as described below.

The atmosphère in the brazing operation can be controlled to assist in achicving a capillary pressure gradient that is suffîcient to drive infiltration of the matrix material over larger/longer distances through the fïller material, such os distances of about 5-7 înches or greater. In each of the embodiments described below and shown in FIGS. 1315 16, the chamber 31 is substantially evacuated prior to mclting of the matrix material 16.

Evacuation at least in the beginning ofthe infiltration process is preferred in one embodiment, In order to avoid oxidation of fïller material. Different procedures may be used in other embodiments, however, such as not evacuating or evacuating to a lesser degree than discussed above.

[0054] FIG. 13 illustrâtes one embodiment ofa system 500 for infiltration, where the infiltration is performed under vacuum conditions. In this embodiment, the entire chamber 31 is evacuated prior to melting of the matrix material 16 and is maintained under vacuum conditions throughout lhe infiltration process. In one embodiment, the gas pressure after évacuation may be from 0.001 to O.OlOTorr, or may be as low os

0.0001 Torr in another embodiment (e.g. 0.0001 to 0.010 Torr), or may be below 0.0001

Torr in a further embodiment. Infiltration may be performed at approximately 21802225°F foraboul 30-60 minutes in oneembodiment. The évacuation ofthe chamber prior to melting of the matrix material 16 reduces or éliminâtes residual gas pressure in the fïller material 15, which assists in driving infiltration through capillary action. It is noted that splattering due to volatil ization of chemicals within the matrix material may be encountered as a resuit of maintaining the system under vacuum after the matrix

material has been melled when certain alloys are used, particularly alloys wilh significant manganèse content. Such splattering can not only damage equipment in the fumace 30, but can also reduce the amount of matrix material 16 available for brazing. This splattering can be mitigated by keeping the Mn content of the alloy sufficiently low, although doing so can be expensive. This splattering can also be uvoided by the presence of Ar or another non-reactive gas in the chamber 31 after the matrix material 16 has been melted.

[0055] FIGS. 14-15 illustrate another embodiment of a system 600 for infiltration, where Ar gas is introduced into the chamber 31 after the matrix material 16 is melted.

As shown in FIG. 14, the chamber 31 Is evacuated as described above prior to the brazing process, as similarly described above with respect to FIG. 13. As described above, infiltration may be performed at approximately 2180-2225’F for about 30-60 minutes in one embodiment. After the matrix material 16 has melted, argon gas 32 (or another non-reactive gas) Is Introduced into the chamber 31. In one embodiment, the Ar 15 gas 32 is fed into the chamber 31 until the Ar partial pressure reaches about 0.050 0.100 Torr. The évacuation of the chamber prior to melting of the matrix material 16 reduces or éliminâtes residual gas pressure in the filier material 15, which assists in driving infiltration as described above, and lhe later introduction of the Ar gas 32 assists in reducing splattering caused by volatile substances. In one example using a system as 20 shown in FIGS. 14-15, the matrix material 16 was found to infiltrate at least 7.5 inches of filier material 15 during infiltration at 2180°F. when the Ar atmosphère was introduced after melting of the matrix material 16. However when the Ar atmosphère was introduced prior to melting, the matrix material 16 was found to infiltrate only 6.5 inches at most, regardless of how long the system was held at the infiltration température. This 25 indicates that residual gas within the filier material 15 may limit the length of infiltration that can be achieved through capillary action.

[0056] FIG. 16 illustrâtes another embodiment of a system 700 for infiltration, where Ar gas 32 is introduced into the chamber 31 prior to melting of the matrix material 16.

As similarly described above with respect to FIG. 14, the chamber 31 in this embodiment 30 is evacuated as described above during the heating process until the system nearly reaches the melting température of the matrix material 16 (e.g. until the température

reaches about 2150T for ductile iron). At that point, Ar gas 32 or other non-reactive gas is introduced into the chamber 31 prior to melting of the matrix material 16. As similarly described above, lhe gas 32 may be introduced until a partial Ar pressure of 0.050 0.100 Ton* is reached, in one embodiment. As described above, infiltration may be performed at approximately 2! 80-2225^eF for about 30-60 minutes in one embodiment.

In order to avoid residual gas pressure în the fil 1er material 15 limiting Infiltration, the mold 12 is provided with a permeable portion 33 in contact with the filler material 15. The permeable portion 33 may be porous or otherwise gas-permeable, to permit residual gas to escape from the filler material 15 during infiltration, so as not to limit infiltration ofthe matrix material 16. The permeable portion 33 may be provided generally opposite the matrix material 16 to avoid the matrix material 16 covering or sealing the permeable portion 33 to prevent escape ofresidual gas prior to completion ofinfiltration. As described above, the presence of the Ar gas suppresses splattering of the molten matrix material 16. In one example using a system as shown În FIG. 16, with the moid 12 including the permeable portion 33, the matrix material 16 was found to ïnfiltrate at least 7.5 inches of fiiler material 15 during infiltration at 2225⁴F, when the Ar atmosphère was introduced before melting of the matrix material 16. However when the mold 12 was sealed and the Infiltration front was not in communication with the atmosphère in the chamber 31 after melting of the matrix material 16, infiltration was found to extend only

6.5 inches at most. This indicates that keeping the infiltration front in communication with the atmosphère in the chamber 31 can reduce the limiting effect that residual gas within the fiiler material 15 may hâve on the capiliary action driving force.

[0057] FIGS. 4-5 îllustrate one example embodiment of a system or assembly 100 for forming a wear résistant composite material, and a method utilizing the system or assembly 100. In this embodiment, the substrate 10 (e.g. a point of an excavating tool) is positioned with a cavity 11 of a mold 12, such thaï the mold 12 entraps a volume in the cavity 11 between the inner surface 13 of lhe mold 12 and lhe outer surface 14 of the substrate 10, os shown in FIG. 4. The substrate 10 may be prepared beforehand, such as by clearing and drying lo remove oil or grc as y substances and/or gril blasting using gamet gril lo remove oxide scales and make the surface gralny so lhe matrix material bonds well to lhe substrate 10. The mold 12 may be made from any suitable material, such as a high-melting point metallic material, a ceramic material, or graphite. If

possible, the mold 12 may be welded, brazed, or otherwise connected to lhe outer surface 14 of the substrate 10, such as by weiding at points P. In one embodiment, lhe mold 12 is a steel shell that is welded to the subslrate to create the cavity 11, and may be gril blasted prior to weiding in order to avoid contamination of the mold cavity 11. Such an embodiment is described in greater detail below and shown in FIGS. 19-20. The fi11er material 15 is inserted into the mold cavity 11 in contact or otherwise in communication with the outersurface 14 ofthe substrate 10, such as in the form of a particulate material or a preform, as shown in FIG. 4. The matrix material 16 is placed in communication with the fil 1er material 15 and the outer surface 14 of the substrate. The matrix material

16 muy be posîtioned within the mold cavity 11, such as by simply placing the matrix material 16 on top of the filler material 15 In solid form. as shown in FIG. 4. In one embodiment, the matrix material 16 may be in block or billet form. In another embodiment, the matrix material 16 may be posîtioned in a feeder or injection structure. The system 100 may then be prepared for infiltration, as described above, such as by placing the system 100 in a fumace for heating, which may include an inert atmosphère (e.g. argon). A tray or similar vessel may be used to support lhe system 100 in the fumace, such as a stainless steel tray. During infiltration, the matrix material 16 meils and infiltrâtes downward through ail of the filler material 15, eventually contacling the outer surface 14 of the substrate 10.

[0058] After infiltration has been conducted and lhe system 100 cooled as described above, a part 17 having a composite coating 18 on lhe outer surface 14 is formed, os shown in FIG. 5. The part 17 may bc removed from the mold 12, which may require cutting or breaking the mold 12 away if welded to the substrate 10 and/or bonded to lhe coating 18. The composite coating 18 contains the filler material 15 bound together and connected to the substrate 10 by the matrix material 16. In one embodiment, the filler material 16 may hâve a volume fraction of 5-95% in the composite material 18. In another embodiment, the filler material 16 may hâve a volume fraction of 30-85%. In some embodiments, lhe part 17 may hâve excess matrix material 19 on at least a portion of the outside of lhe composite coating 18. The excess materiai 19 may be Intentionally created and left on the part 17, such as lo serve as a base for weiding or attaching another piece. The excess material 19, if présent, may instead be removed, such as by machining. The composite coating 18 may be formed with wide range of thicknesses,

depending on lhe desired application. In one embodiment, a part 17 may be formed with a composite coating IS that is about 0.5” thick, which may be usable in a wide variety of applications. The part 17 may be a point, edge, or other portion of a piece of equipment that sustains repeated impacts and stress, and the excellent wear résistance and toughness 5 of the composite coating 1S enhances performance in such applications. Excavatîng / miningequipment represents one example of an application fora part 17 produced according to the Systems and methods described herein. FIG. 12 illustrâtes an additional embodiment of a part 17’ produced according to one embodiment of the system and method described herein, in lhe form of a wear member for earthmoving equipment (e.g., 10 a steel mining point) with a working portion forming the substrate 10’ overlaid on ils outer surface 14' with a wear résistant composite material layer 18* as described above. In one embodiment, the composite material layer 18* consists of sphericai cast tungslen carbide particles or other wear résistant material in a ductile iron matrix material.

[0059] FIGS. 17-18 illustrate another embodiment of a substrate IO(e.g. apointof 15 on excavaling or mining tool) that may be used in connection with the system or assembly 100 as shown In FIGS. 4-5, or a similar system/assembly, for produclng a wear résistant composite coating 18. Depending on the identity and nature of the material of the substrate 10, the filler material 15, and/or the matrix material 16, the coefficients of thermal expansion (CTE) of the substrate lOand the coating 18 may be mismatched. For 20 example, when a steel substrale 10 is used, lhe steel typically has a higher CTE thon the coating 18. One example of such a CTE différence may be about 2 x 10⁶ /°C, depending on materials used. This, in lurn, can cause debonding between lhe substrate 10 and the coating 18, particularly when the coating 18 is formed on the outside surface of lhe substrate 10 (e.g. os shown in FIGS. 4-5). In the embodiment of FIGS. 17-18, the 25 substratc 10 is provided with protrusions 28 in lhe form of ribs on the outer surface 14.

The protrusions 28 can assist in mitigating the probiems caused by différences in CTE between the substrate 10 and the coating 18 by plastically deforming in response to lhe pressures exerted as the substrate 10 and the coating 18 cool after brazing. In one embodiment, the protrusions 28 may be formed of a material with a rciatively low yield 30 strength and good ductility in order to case plastic deformation. Other considérations in selecting the material for the protrusions 28 are ils compatibility for connection to the substrate 10 (e.g. by welding or other technique) and for bonding to the coating 18. One

example of material suitable for use as protrusions bonded to a steel substrate 10 is müd steel, such as AISI 1008. Other examples ofsuitable materials may include 304 stainless steel, AISI 1018, and AtSI 1010, among others. The protrusions 28 also provide additional surfaces forbondingofthe coating 18, and maytherefore further enhance bonding between the coating 18 and the substrate 10. As seen in FIG. 18, the coating 18 forms around the protrusions 28 such that the protrusions 28 are embedded within the coating 18 and bonded to the coating 18 in the finished part 17. However in other embodiments, the protrusions 28 may extend at least to the outer surface of the coating 18 and may be substantially flush with the outer surface of the coating 18.

[0060] The protrusions 28 in the embodiment of FIGS. 17-18 extend outwardly from the outer surface 14 of the substrate 10 and are in the form of ribs or plates having a length and height significantly greater than their thickness. In one example, the protrusions 28 may hâve a length of about 1-2 inches (parallel to the surface of the substrate 10), a height of about 0.25 inches (parallel to the thickness direction of the coating 18), and a thickness of about 0.125 inches. Additionally, the protrusions 28 ln this embodiment are oriented in a generally axial manner and distributed fairly evenly and symmetrically on ail facets of the outer surface 14 of the substrate 10. In one embodiment, the protrusions 28 may hâve a thickness, length, and width selected in such a way that some or ail of the strain resulting from thermal expansion mismatch is accommodated by deformation of the protrusions 28. Additionally, in one embodiment, the length of each protrusion may be greater than the height, which may in tum be greater than the thickness (i.e., length>wîdth>thickness). Protrusions 28 using this dimensional relationship increase potential bonding area for the coating 18, as the potentlal bonding area added by the protrusion 28 is greater than the potential bonding area of the substrate 10 covered by the protrusion 28. The dimensions ofthe protrusions 28 may be modified depending on the thickness of the coating and dimensions of the substrate. The distance between the protrusions 28 may also dépend on the location and geometry of the substratc 10, and can vary from Γ to 3” in one embodiment. In other embodiments, the protrusions 28 may hâve a different form, such us rods, cônes, pegs, etc., and may be distributed and/or oriented in a different manner. The protrusions 28 as shown in FIG. 17 are welded tothe outer surface 14 of the substrate 10. The substrate 10 may be gril blusted after welding. Other techniques for connecting the protrusions 28 to

the substrate 10 may be used in other embodiments. It is understood that, the protrusions 28 may be formed of the same material as lhe substrate 10, and may be integrally formed with lhe substrate 10 in one embodiment. It is also understood that lhe substrate 10 having the protrusions 28 may require a heat treatment or modified versions of traditional heat treatments after welding and/or after brazing, depending on the materials and structures used. Further, the finished part 17 as shown in FIGS. 17-18 is a wear member, such as a point for earthmoving equipment, and the substrate 10 is formed by a working portion of the wear member, such thaï the protrusions 28 are connected to the working portion. It is understood that other types ofprotrusions 28 may be utilized with 10 such a wear member, and also that protrusions 28 as shown in FIGS. 17-18 may be utilized with other types of articles of manufacture.

[0061] FIGS. 6-9 illustrate other Systems and methods for creating a wear résistant composite according to aspects of the invention. FIGS. 6-7 illustrate a system 200 for forming a composite material on an inner surface 20 of a substrate 10 through outward or 15 radial infiltration. In this embodiment, the subsirate 10 is tubular In form, and lhe substrate 10 is used along with a mold 12 and a plate 21 tocreote a mold cavity 11 on lhe inside of the substrate 10. The plate 21 may bc formed ofany suitable material, including any material mentioned above for mold construction (e.g. graphite, métal, or ceramic). If lhe plate 21, lhe mold 12, and/or the substrate 10 arc made of weldable materials, any of these components may be connected by welding, however welding is not necessary. The porous filler material 15 is positioned on the innersurface 20 ofthe substrate 10 in position to form the composite, and the matrix material 16 is placed in contact or otherwise in communication with the filler material 15. Ceramic bcads 22 or another displacement material are also placed in the mold cavity 11, in position to displace lhe matrix material 16 during infiltration. It is understood that the displacement of the matrix material 16 is done in order to support lhe matrix material 16 in constant contact with lhe filler material 15 during infiltration, and that the infiltration of the matrix material 16 is primarily driven by other forces (e.g. capillary action), rather than force exerted by the ceramic beads 22. Altemately, another displacement technique may be used. In the embodiment in FIGS. 6-7, the matrix material 16 may be placed in the mold cavity 11 in tubular form (see FIG. 7), in contact with lhe filler material 15, and infiltrâtes outwardly into lhe filler material 15. The matrix material 16 may instead be provided as a plurality of billets arranged in a circular formation around the filler material 15 in another embodiment. In this configuration, the ceramic beads 22 are placed inside the inner diameter of the tubular matrix material 16, and the beads 22 move outwardly to displace the infiltrated matrix material 16. Altemately, another displacement technique may be used. The system 200 can be placed in a fumace and processed as described above to complété infiltration. The resulting part has a ceramic material on the innersurface 2! ofthe substrate, and may includeexcess matrix material, as described above.

[0062] FIG. 8 illustrâtes a system 300 for forming a composite material on an outer surface 14 of a substrate 10 through both horizontal and downward vertical infiltration. In this embodiment, a portion of the substrate 10 is placed inside the mold cavity ! t, and a plate 2! is used with the mold 12 to enclose the mold cavity 11. The plate 2! may be formed of any suitable material, including any material mentioned above for mold construction (e.g. graphite, métal, orceramic). lf the plate 21, the mold !2, and/orthe substrate 10 are made of weldable materials, any of these components may be connected by welding, however welding is not necessary. An additional member 23 may be used for sealing purposes and/or for terminating infiltration, and may be positioned adjacent the plate 2 !. Graphite foil or ceramic woo! may be used as the additional member 23 to accomplish these functions, as the matrix material 15 does nol wet or penetrate these materials. The porous filler material 15 is positioned on the outer surface 14 of the substrate 10 in position to form the composite, and the matrix material 16 is placed in contact or otherwise in communication with the filler material 15. As shown in FIG. 8, the matrix material 16 îs placed above the filler material 15 for downward infiltration and alongsîde the filler material 15 for horizontal infiltration. Ceramic beads 22 or another displacement material are also placed In the mold cavity 11, in position to displace the matrix material 16 during infiltration. Altemately, another displacement technique may be used. In the embodiment in FIG. 8, lhe matrix material 16 is placed in the mold cavity ! t around lhe filler material 15, and infiltrâtes horizontal ly and vertically into the filler material 15. In this configuration, the ceramic beads 22 are placed horizontally around the matrix material 16, and the beads 22 move inwardly to displace lhe horizontally infiltrated matrix material 16. A barrier 24, such as a flexible ceramic fiber mat or a woven fabric, may be placed between the beads 22 and the matrix material 16.

The barrier 24 may generally be imperméable to the molten matrix material 16. and may also be flexible and may transmit pressure from the ceramic beads 22 onto the matrix material 15. No displacement of the vertically Infiltrated matrix material 16 is necessary. The system 300 can be placed in a fumace and processed as described above to complété 5 infiltration. The resulting part has a ceramic material on the outer surface 14 ofthe substrate, and may include excess matrix material, as described above.

[0063] FIG. 9 illustrâtes a System 400 for forming a composite material on an outer surface 14 of a substrate 10 through both horizontal and downward vertical infiltration.

In this embodiment. a portion of lhe substrate 10 Is placed inside the mold cavity 11, and 10 a plate 21 i s used with lhe mold 12 to enclose the moldcavily II. The plate 21 maybe formed of any suitable matériel, including any material mentioned above for mold construction (e.g. graphite, métal, or ceramic). If the plate 21, the mold 12, and/or the substrate 10 are made of weldable materials, any of these components may be connected by welding, however welding is not necessary. An additional member 23 may be used 15 for sealing purposes and/or for terminating infiltration, and may be positioned adjacent the plate 21. Graphite foi) or ceramic wool may be used as the additional member 23 to accomplis!! these fonctions, as the matrix material 15 does not wet or penetrate these materials. The porous filler material 15 is positioned on the outer surface 14 of the substrate 10 in position to form the composite, and the matrix material 16 is placed in 20 contact or otherwise in communication with the filler material 15. As shown in FIG. 9, the matrix material 16 is placed above the filler material 15 fordownward infiltration and alongside the filler material 15 for horizontal infiltration. Ceramic beads 22 or another displacement medium are also placed in the mold cavity 11, in position to displace the matrix material 16 during infiltration. Altemately, another displacement technique may 25 be used. In the embodiment in FIG. 9, the matrix material 16 is placed in the mold cavity 11 around the filler matériel 15, and infiltrâtes horizontalIy and vertically into the filler material 15. In this configuration, the ceramic beads 22 are placed horizontally and vertically around the matrix material 16, and the beads 22 move inwardly and downwardly to displace the infiltrating matrix material 16. The system 400 can be 30 placed in a fumace and processed as described above to complété infiltration. The resulting part has a ceramic material on the outer surface 14 of the substrate, and may include excess matrix material, as described above.

[0064] FIGS 19-20 illustrate another example of a system 800 for forming a composite material on an outer surface 14 of a substrate 10 mainiy through downward vertical infiltration. The system 800 of FIGS. 19-20 utilizes a mold in the form of a shell 314 made from a sheet material, which is shown being used in conjunction with a substrate 312 in the form of an excavating/mining point that may be similar to the substrates 10.10' as shown in FIGS. 4-5 and 12. The shell 314 shown in FIGS. 19-20, along with other such shells, are described in greater detail in U.S. Provisional Application No. 61/472,470, filed April 6,2011, and U.S. Patent Application Serial No. 13/440,273, filed April 5,2012, and pubiished as U.S. Patent Application Publication

No. 2012/0258273 on October 11,2012, which applications are incorporated by reference herein in their entireties and made parts hereof. The shell 314 may be utilized to form a composite coating 18 as similarly described above and shown in FIGS. 4-5. In one embodiment, the filler material 15 may be poured through the opening 317 in the shell 314, and the matrix material 16 may thereafter be placed on top of the filler material 15, as similarly shown in RG. 4. The opening 317 may hâve a funnel-like configuration to aid insertion oflhe filler material 15 and/or the matrix material 16. In other embodiments, the opening 317 may be located elsewhere on the shell 314, such as if the shell 314 is positioned in a different orientation during brazing.

[0065] The sheet métal of the shell 314 may be made of any material capable of being formed or fabricated to a particular desired shape and capable of withstonding dissolution, melting, orundue weakening by the infiltrating material. or generaily by the températures required for infiltration brazing, during the infiltrating process. In one example, the shell 314 may be formed of low-carbon “mild” steel. For example, shell 314 may hâve an average shell thickness of approximately 0.105 in. In one embodiment, the shell 314 may be made of sheet métal In the range of 16 Ga (0.060 in. thick) to 10 Ga (0.135 in. thick), which may be useful fora wide range ofapplications. In contrast, the substrate 312 in FIG. 20 may hâve a thickness ranging from 1.000 to 3.450 inches in lhe région covered by the shell. In other embodiments, the shell 314 may hâve any other suitable thickness. For example, in further embodiments, the shell 314 may be made of a steel or other metallic plate having a thickness of approximately 0.25 Inches, or may be cast, machined from bar stock, or formed in a different manner. It is understood that different portions of the shell 314 may hâve different thicknesses.

[0066] The relative thinness of lhe shell 314 when compared to the substrate 312 means that the shell 314 may be formed easily, relatively inexpensively. For simple shapes of a shell, a relatively low-cost shell 314 may be made by cutting pièces of sheet métal, and weiding or brazing those pièces together. Slightly more complicated shapes may be made by bending pièces of sheet métal in particular configurations, and then weiding the bent sheet métal pièces together. Complex shapes can be made by sheet métal forming processes such as deep drawing, forming by the Guérin process (rubber pad forming), hydroforming. and/or explosive forming. Précision ('lost wax) casting could be used as well, although lhe cost ofthe lost wax process would often be uneconomical. For particularly complicated shapes, pièces of the shell could be formed by one or more of these processes, and then joined by weiding or brazing.

[0067] As shown in FIGS. 19-20, lhe shell 314 is formed of two parts, having a twopart conformai band 320. A two-part shell body 316 ofshell 314 may be inïtially formed from a front half piece 326 and a back half piece 328, having a front flange 330 or a rear 15 flange 332, respectively. Front flange 330 exlends transversely from lhe back edge of the front half 326 and rear flange 332 extends transversely from the front edge ofthe back half 328. Front flange 330 may be joined to rear flange 332 by weiding or brazing with a brazing material having a higher melting température than the material intended for infiltration. The shell 314 may hâve a conformai band 320 configured to be placed în 20 surface-to-surface contact with a portion of the surface of the substrate 312 around an entire periphery of the shell 314, such that the shell 314 is connected to the substrate 312 by weiding or brazing at least at the conformai band 320, as described below. In olher embodiments, the shell 314 may be formed of a single piece (in which flangcs 330,332 may not be présent) or a larger number of pièces. The two-part shell 314 may be more easily formed than a corresponding one-part shell, in certain configurations. The two-part shell 314 may also be more easily joined to a corresponding substrate, in certain configurations, when compared to such joining with a corresponding one-part shell.

[0068] The shell 314 is shown joined to a portion of a corresponding substrate 312 in the form of a point, in FIG. 20. An outer geometiy for substrate 312 may include a primary body 334 that defines a bonding surface 335 for weiding or brazing to the conformai band 320. The substrate 312 may provide at least some recess or other relief

for the bonding of the hard material, such as a plateau 336 and (he surrounding surfaces. A distal end of the substrate 312 may be shaped (o defîne an angular edge 344, and/or a rounded face 346. In another embodiment, the substrate 312 may not provide any recess or other relief for the hard material. As seen in FIG. 20, the shell 314 extends smoothly 5 away from the conformai band 320, defining a cavity 350 between substrate 312 and shell 314. The cavity 350 defines a resulting thickness ofthe coating (not shown) bonded to substrate 312, and lhe inner geometry of the shell 314 defines an ultimute outer geometry of a fînished part.

[0069] The light sheet métal shell 314 as shown in FIGS. 19-20 may be readily moved for précisé alignment on a substrate, and then welded (o (he substrate, regardless of most orientations of the substrate. The thin métal shell is easy to attach reliably to the underlying substrate by welding or high température brazing, without the need for clampîng or fixants, and the Joint created is fluid-tight even at the high températures required for infiltration brazing. In any type of infiltration hardfacing involving molds, the molten métal brazing material should romain inside the mold. With the thin métal shells of (he prosent disdosure, re liable attachment to a substrate is achieved without extra clamping or fixtures. The resulting assembly is therefore more eastly placed ln a fumace for infiltration brazing, allowing substantially greater case of infiltration hardfacing heavy items.

[0070] It is understood that various features of the Systems 100,200,300,400,500,

600,700,800 described above and shown in lhe figures, as well as variations thereof, may be combined and tnterchanged within the scope of the présent invention. Likewise, any of the techniques of the methods described above, or variations thereof, may be utilized in connection with any of the Systems 100,200,300,400,500,600,700,800 25 described above.

[0071] FIGS. 10-11 illustrale photomicrographs of a composite material 18 formed using a system similar (o the system 100 of FIG. 4 and using a method as described above. FIGS. 10-11 illustrate the spherical cast WC Aller material 15 surrounded by a ductile iron matrix material 16. The matrix material 16 includes graphite nodules 25, 30 which is characteristic of ductile iron. As seen in FIGS. 10-11 the spherical shapes of most of the WC particles 15 hâve been preserved, indicating minimal reaction or

dissolution ofthe fiiter material 15 with the molten matrix material 16. FIG. 11 illustrâtes the interface 26 between the composite material 18 and the excess matrix material 19.

[0072] Composite coatings produced according to the Systems and methods described herein exhibil excellent wear résistance and toughness. In one example, samples were prepared using a system similar to the system 100 of FIG. 4 and using a melhod as described above, using spherical cast WC, crushed cast WC, and cemented WC with a ductile iron matrix. Samples of cast and cemented WC reinforced with nickel based alioys and copper by vacuum Infiltration ai 2050°F were prepared for comparison.

D2 steel was also used for comparison. Dry sand rubber wheel (DSRW) abrasion tests (ASTM G65) were conducted on these samples, pursuant to Procedure A of ASTM G65. The test conditions were as follows:

• Total révolutions : 6000 • Load on the sample: 30 Ibs · Sand flow rate : 300-400 g/mïn.

[0073] Two consecutive DSRW tests were done on the same wear scar région and the mass loss during the second test was taken as représentative of abrasive wear loss of material. As it can be seen from Table 1 below, spherical cast tungsten carbide/ductile iron followed by crushed cast tungsten carbide /ductile iron showed excellent abrasion 20 résistance compared to other materials. The samples were prepared us coatings, and the substrate was removed by machinîng and grinding in order to expose the surface close to the substrate for testing.

Table 1: Dry sand rubber wheel (DSRW) (est data on different materials

SI. No	Carbide material	Mass loss, g	Calculated density, g/cc	Volume loss, mm¹	Rockwell Hardness, HRC
1	Spherical cast WC/DI	0.03	12.18	2.46	50
2	Crushed cast WC/DI	0.06	12.18	4.93	45
3	Cemented carbide/DI	0.19	10.95	17.3S	57
4	Spherical cast WC/NI-7Cr-3Fe4.5SI-3.1B	0.19	12.58	15.10	55
S	Cemented carblde/Nl-7Cr3Fe-4.SSI-3.lB	0.10	11.37	8.79	51
6	Crushed cast WC/Nl-7Cr-3 Fe4.551-3.16	0.14	12.58	11.13	50
7	Crushed cast WC/Cu	0.08	13.02	6.14	5
8	Cemented carblde/Cu	0.37	11.83	31.28	9
9	D2 tool steel	0.25 \|	7.8	32.05	60

[0074] As seen from the results in Table l above, the use of ductile iron in combination with spherical cast WC and crushed cast WC resulted in lower mass and volume loss as compared to other combinations. Additionally, lhe combinations of WC and ductile iron had hardnesses that were comparable to other combinations. Further, ductile iron is considerably less expensive than the other matrix alloys tested, particularly Ni and Cu alloys. Accordingly, this test ing illustrâtes the ad vont âge ou s use of a composite made from a ductile iron matrix material and WC filler material using Systems 10 and methods according to embodiments of lhe présent invention.

[0075] The various embodiments of the System, method, and product described herein provide benefits and advanlages over exîsting technology. For example, the résultant composite product exhibits excellent wear résistance and ioughness, and can be produced economically. As another example, the system and method can be used to 15 apply a wear résistant material to a large variety of different substrates, including wrought, cast, and powder melallurgy métal! ic substrates, as well as non-metallic

substrates such as ceramics or ceramïc-based composites, as long as the melting point of the material ts suitable for the infiltration process. As another example, the use of brazing techniques allows for the material formation and bonding to the substrate to be accomplished in a single step. Additionally, the brazing techniques typicaily utilize a 5 longer time for infiltration as compared to casting and other techniques, which in tum allows for longer infiltration lengths (up to 8-10” or greater in some embodiments). Accordingly, thicker coatings can also be produced as compared to existing techniques, including casting, as well as other hardfacing processes such as plasma transferred arc weld overlay, thermal spray, etc. As another example, the system and method may 10 utilize lower superheating than other processes (e.g. casting), which results in less reaction between the filler material and the matrix material and sound microstructures that exhibit high wear résistance and toughness. In addition, the lower degree of reaction permits smalier particle sizes, or multiple partiele sizes, to be used for the filler material, by which greater density of the hard filler material can be achieved. As described above, 15 greater yield strength of the matrix material and greater overall wear résistance of the composite material can also be achieved. As another example, the use of an inert atmosphère in the System and method minimizes or prevents oxidation of the components and can control the évaporation of volatile éléments from the matrix material, reducing splashing. Still other benefïts and advantages are recognized by those 20 skilled in the art.

[0076] Several alternative embodiments and ex amples hâve been described and illustrated herein. A person ofordinary ski!! in the art would appreciate the features of the individual embodiments, and the possible combinations and variations ofthe components. A person ofordinary skill in the art would further appreciate that any of the 25 embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other spécifie forms without departing from the spirit or central characteristics thereof. The présent examples and embodiments, therefore, are to be considered in al! respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.

Relative terms such as top,” bottom,” etc., as used herein, are intended for illustrative purposes only anddo not limit the embodiments in any way. Nothing in this spécification should be construed as requiring a spécifie three dimensional orientation of

structures in order to Tall within the scope of this invention, unless specifically recited in the claims. Also, the reader is advised that the attached drawings arc not necessarily drawn to scale. Additionally, the lcrm “plurality,” as used herein, indicates any number greater than one, either disjunctïvely or conjunctively, as necessary, up to an infinité 5 number. Further, “Providing an article or apparatus, as used herein, refers broadly to making the article available or accessible for future actions to be performed on the article, and does not connote that the party providing the article has manufactured, produced, or supplied the article or that the party providing the article has ownership or control ofthe article. Accordingly, while spécifie embodiments hâvebeen illustrated and 10 described, numerous modifications corne to mind without significantly departing from the spîril of the invention and the scope of protection is only limited by the scope ofthe accompanying Claims.

Claims

What is claimed is:

L A method comprising:

positioning a mold proximate a surface of a substrate, such that the surface is in 5 communication with a cavity of the mold;

placing a porous wear résistant material within the cavity, in close proximity to the surface;

placing a metallic matrix material in communication with the cavity, wherein the matrix material comprises ductile iron; '

10 heating the mold and the matrix material to a température above a melting point of the matrix material and holding the température above the melting point for a time sufficient for the matrix material lo înfiltrate the wear résistant material in molten form and contact the surface of the substrate;

cooling the mold and the matrix material to solidify the matrix material and form 15 a wear résistant composite coating comprising the wear résistant material embedded within lhe matrix material on lhe surface of the substrate.
2. The method of claim 1, wherein the ductile iron of lhe matrix material has a composition comprising, in weight percent, approximately 3.0-4.0% carbon, approximately 1.8-2.8% silicon, approximately 0.1-1.0% manganèse, approximately

20 0.01-0.03% sulfur, and approximately 0.01-0.1% phosphorous, with the balance being iron and incidcntal éléments and impurities.
3. The method of claim I, wherein the wear résistant material comprises one or more materials selected from lhe group consisting of: carbides, ni (rides, bondes, silicides, intermctallic compounds of transition metals, and combinations thereof.

25
4. The method of claim 3, wherein the wear résistant material comprises one or more carbides selected from the group consisting of: WC, TiC, SiC, CrjCj, VC, ZrC, NbC, TaC, (W,Ti)C, B4C, and Mo?C, and combinations thereof.
5. The method of claim 3, wherein the wear résistant material comprises one or more nitrides selected from the group consisting of: TiN, BN, SijNj, ZrN, VN, TaN, 30 NbN, HfN, CrN, MoN, and WN, and combinations thereof.
6. The method of claim 3, wherein the wear résistant material comprises one or more borides selected from the group consisting of: titanium boride, chromium boride, tungsten boride, nickel boride, zirconium boride, hafnium boride, tantalum boride, niobium boride, vanadium boride, molybdenum boride, silicon boride, aluminum boride,

5 and other borides of transition metals, and combinations thereof.
7. The method of claim 3, wherein the wear résistant material comprises one or more silicides of transition metals.
8. The method of claim I, wherein lhe wear résistant material has a wettlng compatible coating.
10 9. The method of claim I, wherein the composite coating is formed on a plurality of surfaces of the substrate.

10. The method of claim 1, wherein the composite coating is formed on only a portion of the surface of the substrate.
11. The method of claim 1, wherein the porous wear résistant material is in the form

15 of a porous preform formed of a parti eu late material bonded together to form the porous preform.
12. The method of claim 11, wherein lhe parti eu late material is bonded together by sintering.
13. The method of claim 11, wherein the part icu laie material is bonded together by a

20 polymer material, wherein lhe température is sufficîent to remove lhe polymer material from the particulate material during heating.
14. The method of claim 1, wherein the mold comprises a sheet métal shell connected to the substrate to defïne the cavity, wherein the shell has an opening to an exterior of the shell, and wherein the porous wear résistant material is placed within the cavity by

25 insertion through the opening.
15. The method of claim 1, wherein the porous wear résistant material is in lhe form of a loose particulate material.
16. The method of claim 1, wherein the heating is performed within a fumace chamber, the method further comprising:

30 evacuating the chamber prior to the température reaching the melting point of the matrix material.
17. The method of claim 16, further comprising:

introducing an inert gas into the chamber after the matrix material has melted.
18. The method of claim 16, wherein the mold has a permeable portion in contact with the porous wear résistant material, the method further comprising:

introducing an inert gas into the chamber before the matrix material has melted.
19. A system comprising:

5 a substrate having a surface;

a mold positîoned in proximity to the surface of the substrate, such that the surface is in communication with a cavity of the mold;

a porous wear résistant material within the cavity, in close proximity to the surface; and

10 a me ta! lie matrix material in communication with the cavity, wherein the matrix material comprises ductile iron;

wherein the system is configured for:

heating the mold and the matrix material to a température above a melting point of the matrix material and holding the température for a time sufficient for 15 the matrix material to infiltrate the wear résistant material in molten form and contact the surface ofthe substrate;

cooling the mold and the matrix material to solidify the matrix material and form a wear résistant composite coating on the surface of the substrate.
20. The system of claim 19, wherein the ductile iron of the matrix material has a 20 composition comprising, in weight percent, approximately 3.0-4.0% carbon, approximately 1.8-2.8% silicon, approximately 0,1-1.0% manganèse, approximately 0.01-0.03% sulfur, and approximately 0.01-0.1% phosphorous, with the balance being iron and incidental eiements and impurities.
21. The system of claim 19, wherein the wear résistant material comprises one or 25 more materials selected from the group consisting of: carbides, nitrides, bondes, silicides, intermetallic compounds of transition metals, and combinations thereof.
22. The system of claim 21, wherein the wear résistant material comprises one or more carbides selected from the group consisting of: WC, TiC, SiC, CrjC?, VC, ZrC, NbC, TaC, (W,TÎ)C, BjC, and MojC, and combinations thereof.

30
23. The system of claim 21, wherein the wear résistant material comprises one or more nitrides selected from the group consisting of: TiN, BN, S13N4, ZrN, VN, TaN, NbN, HfN, CrN, MoN, and WN, and combinations thereof.
24. The system of claim 21, wherein lhe wear résistant material comprises one or more bondes selected from lhe group consisting of: titanium bonde, chromium bonde, lungsten bonde, nickel bonde, zirconium bonde, hafnium bonde, tanlalum boride, niobium boride, vanadium boride, molybdenum boride, silicon boride, aluminum boride,

5 and other bondes of transition metals, and combinations thereof.
25. The system of claim 21, wherein the wear résistant material comprises one or more silicides of transition metals.
26. The system of claim 19, wherein the porous wear résistant material is in the form of a porous preform formed of a particulate material bonded together to form lhe porous

10 preform.
27. The system of daim 19, wherein the porous wear résistant material is in the form of a loose particulate material.
28. An article of manufacture comprising:

a metallic substrate having a surface with a wear résistant composite coating

15 bonded to the surface, wherein the wear résistant composite coating comprises:

a porous wear résistant material;

a metallic matrix material intermixed with the wear résistant material, the matrix material further being bonded to the surface of the substrate to bond the wear résistant composite coating to the substrate, wherein the metallic matrix 20 material comprises ductile iron.
29. The article of claim 28, wherein lhe ductile iron of the metallic matrix material has a composition comprising, in weight percent, approximately 3.0-4.0% carbon, approximately 1.8-2.8% silicon, approximately 0.1-1.0% manganèse, approximately 0.01-0.03% sulfur, and approximately 0.01-0.1% phosphorous, with the balance being

25 iron and incidental éléments and impurities.
30. The article of daim 29, wherein lhe composition of the metallic matrix material further comprises up to 37 wt.% nickel.
31. The article of claim 29, wherein the composition of the metallic matrix material further comprises up to 5.5 wt.% chromium.

30
32. The article of claim 29, wherein the composition of the metallic matrix material further comprises upto5.5 wt.% silicon.
33. The article of daim 28, wherein lhe coating has a thickness of at least 73 inches.
34. The article of claim 28, wherein the coating has a thickness that is greater than a thickness of the substrate.
35. The article of claim 28, wherein the article is a point for earthmoving equipment.
36. The article of daim 28, wherein the wear résistant material is a particulate

5 material, and the metalltc matrix material bonds the wear résistant material together.
37. The article of claim 28, wherein the wear résistant material comprises one or more materials selected from the group consisting of: carbidcs, nttrides, borides, silicidcs, intermctallic compounds of transition metals, and combinations thereof.
38. The article of daim 37, wherein the wear résistant material comprises one or

10 more carbidcs selected from lhe group consisting of: WC, TiC, SiC, CrjCj, VC, ZrC, NbC, TaC, (W,Ti)C, B4C, and MojC, and combinations thereof.
39. The article of claim 37, wherein lhe wear résistant material comprises one or more nitrides selected from the group consisting of: TiN, BN, SiîNi, ZrN, VN, TaN, NbN, HfN, CrN, MoN, and WN, and combinations thereof.

15
40. The article of claim 37, wherein the wear résistant material comprises one or more borides selected from the group consisting of: titanium boride, chromium bonde, tungsten boride, nickel boride, zirconium boride, hafnium boride, tantalum boride, niobium boride, vanadium boride, molybdenum boride, silicon boride, aluminum boride, and other borides of transition metals, and combinations thereof.

20
41. The article of claim 37, wherein the wear résistant material comprises one or more silicides of transition metals.
42. The article of claim 28, wherein the substrate has a plurality of protrusions connected to the surface and extending outwardly from the surface, and wherein the protrusions are embedded within the wear résistant composite coating.

25
43. The article of claim 42, wherein the protrusions comprise a plurality of rib members symmetrically distributed on the outer surface of the substrate.
44. A wear member for earthmoving equipment comprising a workîng portion and a composite coating overlayîng lhe workîng portion, the coating comprising a porous wear résistant material and a ductile iron matrix material intermixed with the wear résistant

30 material, wherein the matrix material bonds lhe coating to the workîng portion.
45. The wear member of claim 44, wherein the ductile iron has a composition comprising, in weight percent, approximately 3.0-4.0% carbon, approximately 1.8-2.8% stlicon, approximately 0.1-1.0% manganèse, approximately 0.01-0.03% sulfur, and approximately 0.01*0.1% phosphorous, with the balance being iron and incidenial éléments and impurities.
46. The wear member of daim 45, wherein the composition of the ductile iron further comprises up to 37 wt.% nickel.

5
47. The wear member of claim 45, wherein the composition of the ductile iron further comprises up to 5 J wt.% chromium.
48. The wear member of claim 45, wherein the composition of lhe ductile iron further comprises up to 5.5 wt.% silicon.
49. The wear member of daim 44, wherein the wear résistant material is a particulate 10 material, and the matrix material bonds the wear résistant material together.
50. The wear member of daim 44, wherein lhe wear résistant material comprises one or more materials selected from the group consisting of: carbides, nitrides, bondes, silicides, intermet allie compounds of transition tnetals, and combinations thereof.
51. The wear member of daim 44, wherein the substrate has a plurality of protrusions

15 connected to the working portion and extending outwardly from the working portion, and wherein the protrusions are etnbedded within the composite coating.
52. The wear member of daim 51, wherein the protrusions comprise a plurality of rib members symmetrically distributed on the working portion.
53. The wear member of claim 44, wherein the coating has a thickness that is greater 20 than a thickness of the substrate.
54. The wear member of claim 44, wherein the coating has a thickness of at least 7.5 inches.
55. A method comprising:

positioning a mold proximale a surface of a substrate to define a cavity;

25 placïng a porous wear résistant material within the cavity;

placing a metallic matrix material in communication with the cavity;

melting the matrix material to form a molten matrix material, by heating within a fumace chamber to a température above a melting point of the matrix material, wherein the melting is performed in a vacuum;

30 holding the température above the melting point until the molten matrix material infiltrâtes the wear résistant material;

cooling the matrix material to solidify the molten matrix material and form a wear résistant composite coating comprising the wear résistant material embedded within the matrix material on the surface of the substrate.
56. The method of claim 55, wherein the vacuum is maintained at least until the

5 molten matrix material infiltrâtes lhe wear résistant material.
57. The method of claim 55, further comprising:

introducing an Inert gas into the chamber after the matrix material has been melted.
58. The method of claim 57, wherein the inert gas has a partial pressure of about

10 0.050-0.100 Torr.
59. A method comprising:

postiioning a mold proximate a surface of a substrate to define a cavity, wherein the mold has a permeable portion;

placing a porous wear résistant material within the cavity, such thaï the

15 permeable portion is in contact with the wear résistant material;

placing a met al lie matrix material in communication with the cavity;

melting the matrix material to form a molten matrix material, by heating within a fumace chamber to a température above a melting point of the matrix material, in the presence of an Inert gas;

20 holding the température above the melting point until the molten matrix material infiltrâtes the wear résistant material, wherein residual gas within the wear résistant material can escape through the permeable portion;

cooling the matrix material to solidify the molten matrix material and form a wear résistant composite coating comprising the wear résistant material embedded within 25 the matrix material on the surface of the substrate.
60. The method of claim 59, wherein the inert gas has a partial pressure of about 0.050 - 0.100 Torr.
61. The method of claim 59, further comprising evacuating the chamber prior to introducing the inert gas into the chamber.

30
62. A method comprising:

positioning a mold proximate a surface of a substrate to define a cavity;

placing a porous wear résistant material within the cavity;

placing a metallic matrix material in communication with the cavity, wherein the matrix material is positioned laterally to the wear résistant material;

placing a displacement medium adjacent the matrix material, opposite the wear résistant material;

5 melting the matrix material to form a molten matrix material, by heating to a température above a melting point of the matrix material;

holding the température above the melting point until the molten matrix material infiltrâtes the wear résistant material. wherein the displacement medium supports the molten matrix material and displaces the molten matrix material as the molten matrix 10 material infiltrâtes the wear résistant material;

cooling the matrix material to solidify the molten matrix material and form a wear résistant composite coating comprising the wear résistant material embedded within the matrix material on the surface of the substrate.
63. The method of claim 62, wherein the displacement material comprises ceramic 15 beads.
64. The method of claim 62, further comprising placing a barrier between the displacement medium and the matrix material.
65. The method of claim 62, wherein the substrate comprises a tubular structure and the surface is an inner surface of the tubular structure, such that the molten matrix

20 material infiltrâtes laterally outward to form the composite coating on the inner surface of the tubular structure, and wherein the displacement medium is placed at a center of the tubular structure and displaces outwardly as the molten matrix material infiltrâtes the wear résistant material.