CA2149010A1 - Abrasion/erosion resistant wear alloy - Google Patents
Abrasion/erosion resistant wear alloyInfo
- Publication number
- CA2149010A1 CA2149010A1 CA 2149010 CA2149010A CA2149010A1 CA 2149010 A1 CA2149010 A1 CA 2149010A1 CA 2149010 CA2149010 CA 2149010 CA 2149010 A CA2149010 A CA 2149010A CA 2149010 A1 CA2149010 A1 CA 2149010A1
- Authority
- CA
- Canada
- Prior art keywords
- alloy
- abrasion
- wear
- erosion resistant
- chromium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000000956 alloy Substances 0.000 title claims abstract description 44
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 43
- 230000003628 erosive effect Effects 0.000 title claims abstract description 24
- 238000005299 abrasion Methods 0.000 title claims abstract description 22
- 239000011159 matrix material Substances 0.000 claims abstract description 21
- 230000008901 benefit Effects 0.000 claims abstract description 9
- 150000001247 metal acetylides Chemical class 0.000 claims abstract description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 16
- 239000011651 chromium Substances 0.000 claims description 14
- 239000000203 mixture Substances 0.000 claims description 14
- 239000000470 constituent Substances 0.000 claims description 13
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims description 12
- 239000011572 manganese Substances 0.000 claims description 12
- 229910052710 silicon Inorganic materials 0.000 claims description 12
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 11
- 229910052750 molybdenum Inorganic materials 0.000 claims description 11
- 239000011733 molybdenum Substances 0.000 claims description 11
- 239000010703 silicon Substances 0.000 claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 10
- 229910052748 manganese Inorganic materials 0.000 claims description 10
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 9
- 229910052742 iron Inorganic materials 0.000 claims description 8
- 229910052759 nickel Inorganic materials 0.000 claims description 8
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 7
- 229910052802 copper Inorganic materials 0.000 claims description 7
- 239000010949 copper Substances 0.000 claims description 7
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 239000011593 sulfur Substances 0.000 claims description 7
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 claims description 6
- 239000012535 impurity Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 description 13
- 229910001566 austenite Inorganic materials 0.000 description 12
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 8
- 229910000734 martensite Inorganic materials 0.000 description 8
- 238000007792 addition Methods 0.000 description 7
- 239000003245 coal Substances 0.000 description 7
- 238000000227 grinding Methods 0.000 description 7
- 235000000396 iron Nutrition 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 229910001037 White iron Inorganic materials 0.000 description 5
- 229910001567 cementite Inorganic materials 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- UFGZSIPAQKLCGR-UHFFFAOYSA-N chromium carbide Chemical compound [Cr]#C[Cr]C#[Cr] UFGZSIPAQKLCGR-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 230000001965 increasing effect Effects 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 235000010755 mineral Nutrition 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000000717 retained effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 229910003470 tongbaite Inorganic materials 0.000 description 3
- 229910001018 Cast iron Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910001141 Ductile iron Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229910001060 Gray iron Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- ZBHWCYGNOTVMJB-UHFFFAOYSA-N [C].[Cr].[Fe] Chemical compound [C].[Cr].[Fe] ZBHWCYGNOTVMJB-UHFFFAOYSA-N 0.000 description 1
- 239000003082 abrasive agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 238000012332 laboratory investigation Methods 0.000 description 1
- 229910001338 liquidmetal Inorganic materials 0.000 description 1
- 238000013332 literature search Methods 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 230000002000 scavenging effect Effects 0.000 description 1
- 238000006748 scratching Methods 0.000 description 1
- 230000002393 scratching effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Crushing And Grinding (AREA)
Abstract
An abrasion/erosion resistant wear alloy suitable for use in high or low stress applications having potential exposure impact loading which provides both good wear characteristics gained from a large volume of high hardness carbides in a tough, stable austenitic matrix which provides requisite ductility and which has the additional advantage of being work hardenable during service.
Description
Case 5504 21~901~
ABRASION/EROSION RESISTANT WEAR ALLOY
FIELD AND BAC~GROUND OF THE INVENTION
The present invention relates, in general, to erosion resistant wear alloys used in industry and, in particular, to an improved abrasion/erosion resistant wear alloy suitable for use in high or low stress applications potentially exposed to impact loading which can be employed in coal or mineral pulverizers or other types of crushing apparatus.
The removal of material from metal surfaces by coal and mineral fragments is a complex process. Several types of abrasive and/or erosive wear can occur in grinding equipment, including gouging abrasion, high stress grinding abrasion, low stress scratching abrasion, and erosion. Erosion is a separate wear mode, distinct from abrasion. Erosion is a ballistic process involving impingement of particles travelling with some velocity while abrasion involves sliding of particles under load over a surface.
Each of the above-described wear modes is influenced in a different fashion by the wear component's material properties and its microstructure. An extensive literature search revealed that in no case has a complete correlation been made between laboratory testing using any type of test method and a wear alloy's performance in the field.
Case 5504 21~90l~
Several factors are relevant to the selection of a wear alloy for a given application. ~ The following discussion involves selection of those properties for optimum wear alloy performance when used in the severe service environment of a coal pulverizer.
Wear alloy performance involves considerations of factors that affect both wear resistance and breakage resistance.
Factors affecting wear resistance include: wear conditions, hardness, carbide volume fraction, matrix microstructure, and carbide morphology. Factors affecting breakage resistance include: load conditions, fracture toughness, austenite content of the matrix, internal stresses, carbide volume fraction (CVF), and carbide morphology.
As discussed in Steam: its qeneration and use, 40th Edition, Copyright ~1992 by The Babcock & Wilcox Company, at page 6-13, cast irons and steels (containing more than 2% or less than 2~ C, respectively) have long had wide acceptance as wear resistant and structural components in boilers. The three types of cast iron used in boilers are white, gray and ductile iron. White cast iron is so known because of the silvery luster of its fracture surface. In this alloy, the carbon is present in combined form as the iron carbide cementite (Fe3C). This carbide is chiefly responsible for the hardness, brittleness and poor machinability of white cast iron. Chilled iron differs from white cast iron only its method of manufacture and it behaves similarly. This type of iron is cast against metal blocks, or chills, that cause rapid cooling at the adjacent areas, promoting the formation o~ cementite. Consequently, a white or mottled structure, which is characterized by high resistance to wear and abrasion, is obtained.
White cast irons can be obtained also through the use of suitable alloy additions. The addition of chromium for example is especially beneficial to cast iron wear properties. High chromium irons have an austenite (or some transformation product 3S of austenite) matrix and an essentially discontinuous complex Ca~e 5504 network of carbides. The M7C3 carbide formed in these materials is considerably harder than the M3C carbide found in most steels.
The replacement of the iron carbide by chromium carbide has a dual effect on material properties. The M7C3 carbide has a S higher hardness than that of quartz, which is one of the most prevalent abrasives in many grinding operations. The higher hardness carbide, therefore, is more resistant to micro-cutting and removal by quartz particles. The morphology of the M,C3 chromium carbide network is typically discontinuous, thereby yielding a less direct fracture path under impact loading.
A significant advance in wear alloy technology occurred in the late 1950s and early 1960s when Ni-Hard IV was developed by INCO. This material is essentially equivalent to B&W's Elverite I cast wear alloy developed specifically for use in pulverizers and other wear resistance parts. The alloy contains approximately 4-7~ nickel and 8-10~ chromium, which produces a discontinuous form of a complex carbide, thereby enhancing its fracture toughness. Subsequent to the development of the Ni-Hard IV, a range of alloys based on the ternary iron-chromium-carbon system with additions of molybdenum and/or copper toenhance hardenability were investigated both in the U.S. and in Europe. During this time period, detailed laboratory investigations determined the boundaries of the ternary Fe-Cr-C
system, as shown in Figs. 1 and 2 which provided a concrete basis for the study and development of improved wear alloy materials.
The chemical compositions of high chromium cast irons typically produce a hypoeutectic alloy which solidifies with a primary austenite (~) matrix, as shown in Fig. 2. Depending upon the alloy chemistry and cooling rates, the matrix can be retained to room temperature or transformation can occur. The alloy can be further modified through the use of an austenite "destablization" heat treatment cycle. This solution treatment precipitates secondary Cr carbides which reduces chromium and carbon levels in the austenite. Thus, upon subsequent cooling Case 5504 21~9~1~
after destablization, a martensitic transformation will occur.
A final tempering step is often utilized to further transform retained austenite within the hardened structure and to stress relieve and temper the already existing martensitic phase.
S VAM 20 , a more recent development, is a 20~ Cr white iron with a molybdenum addition which yields an essentially austenitic material in the as-cast condition. Subsequent thermal processing produces a material with a carbide-in-martensite matrix, very high hardness and good toughness (compared to other white irons). The hardness and wear resistance of VAM 20 are superior to those of the Elverites and similar alloys in part due to the molybdenum addition which forms carbides which are harder than chromium carbide. It is always used in the heat treated condition, which accounts for its good toughness and uniformity. VAM 20 is used in grinding elements of coal pulverizers.
The high Cr-Mo cast wear irons as defined in A.S.T.M. A532 Type IIE have the following chemical composition ranges:
Weiqht Percent Constituent Ranqe Carbon 2.6 - 3.2 Manganese 0. 5 - 1.5 Silicon 1.0 max Nickel 1.5 max Chromium 18.0 - 23.0 Molybdenum 1.0 - 2.0 Copper 1.2 max Phosphorous 0.10 max Sulfur 0.06 max The balance is essentially iron with the usual impurities.
Because the grinding of various materials such as coal requires significant capital expense in machinery and grinding Case 5504 2149Q 10 wear elements, improvements in the durability and wear resistance of these components is a~constant goal. It has thus become desirable to develop a new erosion resistant wear alloy suitable for use in such applications.
5 SUMM~RY OF l~IE INVENTION
A review of the open literature coupled with an assessment of current wear alloys and their in-service performance has led the present inventors to conclude that wear alloy performance can be improved. In particular, improved performance can be obtained by:
(1) modifying the metal matrix by adding elements that stabilize certain microstructural phases (i.e., nickel, molybdenum and carbon are known to stabilize the austenitic phase in ferrous materials);
ABRASION/EROSION RESISTANT WEAR ALLOY
FIELD AND BAC~GROUND OF THE INVENTION
The present invention relates, in general, to erosion resistant wear alloys used in industry and, in particular, to an improved abrasion/erosion resistant wear alloy suitable for use in high or low stress applications potentially exposed to impact loading which can be employed in coal or mineral pulverizers or other types of crushing apparatus.
The removal of material from metal surfaces by coal and mineral fragments is a complex process. Several types of abrasive and/or erosive wear can occur in grinding equipment, including gouging abrasion, high stress grinding abrasion, low stress scratching abrasion, and erosion. Erosion is a separate wear mode, distinct from abrasion. Erosion is a ballistic process involving impingement of particles travelling with some velocity while abrasion involves sliding of particles under load over a surface.
Each of the above-described wear modes is influenced in a different fashion by the wear component's material properties and its microstructure. An extensive literature search revealed that in no case has a complete correlation been made between laboratory testing using any type of test method and a wear alloy's performance in the field.
Case 5504 21~90l~
Several factors are relevant to the selection of a wear alloy for a given application. ~ The following discussion involves selection of those properties for optimum wear alloy performance when used in the severe service environment of a coal pulverizer.
Wear alloy performance involves considerations of factors that affect both wear resistance and breakage resistance.
Factors affecting wear resistance include: wear conditions, hardness, carbide volume fraction, matrix microstructure, and carbide morphology. Factors affecting breakage resistance include: load conditions, fracture toughness, austenite content of the matrix, internal stresses, carbide volume fraction (CVF), and carbide morphology.
As discussed in Steam: its qeneration and use, 40th Edition, Copyright ~1992 by The Babcock & Wilcox Company, at page 6-13, cast irons and steels (containing more than 2% or less than 2~ C, respectively) have long had wide acceptance as wear resistant and structural components in boilers. The three types of cast iron used in boilers are white, gray and ductile iron. White cast iron is so known because of the silvery luster of its fracture surface. In this alloy, the carbon is present in combined form as the iron carbide cementite (Fe3C). This carbide is chiefly responsible for the hardness, brittleness and poor machinability of white cast iron. Chilled iron differs from white cast iron only its method of manufacture and it behaves similarly. This type of iron is cast against metal blocks, or chills, that cause rapid cooling at the adjacent areas, promoting the formation o~ cementite. Consequently, a white or mottled structure, which is characterized by high resistance to wear and abrasion, is obtained.
White cast irons can be obtained also through the use of suitable alloy additions. The addition of chromium for example is especially beneficial to cast iron wear properties. High chromium irons have an austenite (or some transformation product 3S of austenite) matrix and an essentially discontinuous complex Ca~e 5504 network of carbides. The M7C3 carbide formed in these materials is considerably harder than the M3C carbide found in most steels.
The replacement of the iron carbide by chromium carbide has a dual effect on material properties. The M7C3 carbide has a S higher hardness than that of quartz, which is one of the most prevalent abrasives in many grinding operations. The higher hardness carbide, therefore, is more resistant to micro-cutting and removal by quartz particles. The morphology of the M,C3 chromium carbide network is typically discontinuous, thereby yielding a less direct fracture path under impact loading.
A significant advance in wear alloy technology occurred in the late 1950s and early 1960s when Ni-Hard IV was developed by INCO. This material is essentially equivalent to B&W's Elverite I cast wear alloy developed specifically for use in pulverizers and other wear resistance parts. The alloy contains approximately 4-7~ nickel and 8-10~ chromium, which produces a discontinuous form of a complex carbide, thereby enhancing its fracture toughness. Subsequent to the development of the Ni-Hard IV, a range of alloys based on the ternary iron-chromium-carbon system with additions of molybdenum and/or copper toenhance hardenability were investigated both in the U.S. and in Europe. During this time period, detailed laboratory investigations determined the boundaries of the ternary Fe-Cr-C
system, as shown in Figs. 1 and 2 which provided a concrete basis for the study and development of improved wear alloy materials.
The chemical compositions of high chromium cast irons typically produce a hypoeutectic alloy which solidifies with a primary austenite (~) matrix, as shown in Fig. 2. Depending upon the alloy chemistry and cooling rates, the matrix can be retained to room temperature or transformation can occur. The alloy can be further modified through the use of an austenite "destablization" heat treatment cycle. This solution treatment precipitates secondary Cr carbides which reduces chromium and carbon levels in the austenite. Thus, upon subsequent cooling Case 5504 21~9~1~
after destablization, a martensitic transformation will occur.
A final tempering step is often utilized to further transform retained austenite within the hardened structure and to stress relieve and temper the already existing martensitic phase.
S VAM 20 , a more recent development, is a 20~ Cr white iron with a molybdenum addition which yields an essentially austenitic material in the as-cast condition. Subsequent thermal processing produces a material with a carbide-in-martensite matrix, very high hardness and good toughness (compared to other white irons). The hardness and wear resistance of VAM 20 are superior to those of the Elverites and similar alloys in part due to the molybdenum addition which forms carbides which are harder than chromium carbide. It is always used in the heat treated condition, which accounts for its good toughness and uniformity. VAM 20 is used in grinding elements of coal pulverizers.
The high Cr-Mo cast wear irons as defined in A.S.T.M. A532 Type IIE have the following chemical composition ranges:
Weiqht Percent Constituent Ranqe Carbon 2.6 - 3.2 Manganese 0. 5 - 1.5 Silicon 1.0 max Nickel 1.5 max Chromium 18.0 - 23.0 Molybdenum 1.0 - 2.0 Copper 1.2 max Phosphorous 0.10 max Sulfur 0.06 max The balance is essentially iron with the usual impurities.
Because the grinding of various materials such as coal requires significant capital expense in machinery and grinding Case 5504 2149Q 10 wear elements, improvements in the durability and wear resistance of these components is a~constant goal. It has thus become desirable to develop a new erosion resistant wear alloy suitable for use in such applications.
5 SUMM~RY OF l~IE INVENTION
A review of the open literature coupled with an assessment of current wear alloys and their in-service performance has led the present inventors to conclude that wear alloy performance can be improved. In particular, improved performance can be obtained by:
(1) modifying the metal matrix by adding elements that stabilize certain microstructural phases (i.e., nickel, molybdenum and carbon are known to stabilize the austenitic phase in ferrous materials);
(2) using heat treatment to homogenize the metal and to stabilize desired microstructural phases; and (3) increasing carbide hardness and volume using strong carbide formers such as vanadium, tungsten, niobium, tantalum or titanium.
The concept of improving wear performance by increasing carbide hardness has met with mixed results in the past.
~urrently there is a great deal of work was underway in Japan exploring this concept, and initially a great deal of work was underway in the United States and in Europe on this idea but, due to the varied and sometimes poor results obtained, work was abandoned by most U.S. researchers. It is also known that high Ca~e 5504 2l49ol volume fractions of metal carbides can cause embrittlement of martensitic materials under some co~nditions.
It is thus an object of the present invention to balance good wear characteristics, which can be gained from high carbide volumes and a hard matrix, against the ductility needed_in the metal matrix to prevent cracking. Such ductility can be obtained by changing the matrix, i.e., from a martensitic to a stable austenitic matrix which can provide the requisite ductility and has the additional advantage of being work hardenable during service. In-service work hardening of the austenite matrix will be local to the surface and can provide additional wear resistance without sacrificing the component ductility that provides breakage resistance. The abrasion/erosion resistant wear alloy of the present invention is particularly suitable for use in high or low stress applications potentially exposed to impact loading. In contrast to stable austenite, it should be noted that retained, metastable austenite can be detrimental to wear alloy performance. Uncontrolled through-section transformation of the metastable austenite to martensite during service is undesirable because, a significant volume change occurs that can cause cracking.
Accordingly, one aspect of the present invention is drawn to an abrasion/erosion resistant wear alloy suitable for use in high or low stress applications potentially exposed to impact loading and having both good wear characteristics gained from a large volume of high carbide, together with a tough, stable austenitic matrix which provides requisite ductility and which has the additional advantage of being work hardenable during service, the alloy having a constituent composition consisting range essentially of:
æll~Q~
Case 5504 Constituent wt. Percent Carbon about 2.6 - 2.9 Manganese about 0.75 - 1.25 Silicon about 0.50 - 1.0 Nickel about 0.5 max. _ Chromium about 25 - 28 Molybdenum about 1.0 - 6.5 Copper about 0.5 max.
Phosphorous about <0.08 Sulfur about <0.05 with the balance essentially iron with the usual impurities.
Another aspect of the present invention is drawn to a particular composition for an abrasion/erosion resistant wear alloy of the type described above, the alloy having a particular constituent composition consisting essentially of:
Constituent Wt. Percent Carbon about 2.75 Manganese about l.oo Silicon about 0.75 Nickel about 0.2 Chromium about 27 Molybdenum about 6.25 Copper residual amounts Phosphorous residual amounts Sulfur residual amounts with the balance essentially iron with the usual impurities.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the present invention, its operating advantages Case 5504 . 2i~9 0 10 and specific results attained by its uses, reference is made to the accompanying drawings and the fo~llowing description in which preferred embodiments of the invention are disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 is a drawing showing the austenite liquidus surface of the Fe-Cr-C system; and Fig. 2 is a drawing showing a corner of the metastable Fe-Cr-C liquidus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following discussion includes a description of the range and preferred compositions of the abrasion/erosion resistant wear alloy of the present invention. It is to be emphasized that this particular abrasion/erosion resistant wear alloy is suitable for use in high or low stress applications having potential exposure to impact loading. It provides both good wear characteristics gained from a large volume of high hardness carbides, and a tough, stable austenitic matrix which provide requisite ductility and which has the additional advantage of being work hardenable during service. The alloy has a composition consisting essentially of the following elements as set forth in the table below, the first column being the particular constituent, the second column being the preferred range in weight percent of these constituents, while the third column represents the preferred particular composition weight percents of these constituents.
Case 5504 21~91~
g Weiqht Percent Preferred Constituent Ranqe Composition Carbon about 2.6 - 2.9 about 2.75 Manganese about 0.75 - 1.25 about 1 00 - Silicon about 0.50 - 1.0 about 0.75 Nickel about 0.5 max. about 0.2 Chromium about 25 - 28 about 27 Molybdenum about 1.0 - 6.5 about 6.25 Copper about 0.5 max. residualamounts Phosphorous about <0.08 residualamounts Sulfur about <0.05 residualamounts The balance is essentially iron with the usual impurities.
In the above range and preferred compositions, the carbon is added to increased carbide volume and alloy hardness. The manganese is added to control cleanliness (i.e., scavenging embrittling elements such as sulfur). The silicon promotes castabilty while the chromium promotes carbide formation.
Finally, the molybdenum stabilizes the austenitic matrix and forms additional high hardness carbides.
The abrasion/erosion resistant wear alloy can be used as-cast. Alternatively, the alloy can be heat-treated or the composition can be changed within the range and coupled with other material processing can be made to develop an austenitic and/or martensitic structure tailored to a variety of wear conditions. For example, when erosive wear conditions predominate, a martensitic matrix may be preferable. Similarly, under more abrasive conditions, a more austenitic structure may be preferable.
It is preferred that the present invention be heat treated according to a two-step process, the first step during manufacture being an austenization step carried out in a temperature range of approximately 1750F to 1950F, the preferred temperaturè being approximately 1850F, for a Ca~e 5504 21~9~10 sufficient time to thoroughly homogenize the metallic structure throughout the parts being made. 'This step is important in obtaining a completely stable austenitic matrix.
The second step is a lower temperature tempering step S carried out in temperature range of approximately 5~F to 1000F, the preferred temperature being approximately 950F, again for a sufficient time to thoroughly homogenize the tempering effects throughout the parts being made.
Another important aspect of the chemical composition of the present invention is that the relative nominal levels of Manganese (Mn) and Silicon (Si) are maintained such that the weight percent of Mn is greater than the weight percent of Si, i.e., that a ratio of Mn/Si is greater than 1Ø This is important because the manganese addition offsets the loss of material toughness caused by the presence of silicon in the alloy. Whereas silicon is necessary to promote castability by improving liquid metal fluidity; some amount of brittleness is imparted to ferrous alloys by silicon additions.
The present invention provides large carbide volume fractions and high carbide hardness promoting good wear resistance. The austenitic matrix provides good resistance to cracking and breakage resistance and the added benefit of being able to be work hardened at the surface during service. This promotes wear resistance without impairing ductility. The abrasion/erosion resistance wear alloy of the present invention can be used to produce components having substantially longer service life, thereby reducing maintenance and replacement costs. Particular applications where the present abrasion/erosion resistant wear alloy can be used includes coal pulverizers or mineral crushing equipment wear surfaces for both abrasion and erosion-resistant applications It will be further appreciated that although the present abrasion/erosion resistant wear alloy is intended for use in coal grinding and pulverizing equipment, other erosive material handling systems and the like may benefit by employing this Case 5504 214~
alloy. It can also be used for other applications where wear resistance is needed. Examples would include shot blasting equipment, mining equipment, and slurry transport. Accordingly, while in accordance with provisions of the statutes there have been descri~ed herein specific embodiments of the inv~ntion, those skilled in the art will understand that nominal changes may be made in the form of the invention covered by the appended claims to enhance its use in various settings, and that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.
The concept of improving wear performance by increasing carbide hardness has met with mixed results in the past.
~urrently there is a great deal of work was underway in Japan exploring this concept, and initially a great deal of work was underway in the United States and in Europe on this idea but, due to the varied and sometimes poor results obtained, work was abandoned by most U.S. researchers. It is also known that high Ca~e 5504 2l49ol volume fractions of metal carbides can cause embrittlement of martensitic materials under some co~nditions.
It is thus an object of the present invention to balance good wear characteristics, which can be gained from high carbide volumes and a hard matrix, against the ductility needed_in the metal matrix to prevent cracking. Such ductility can be obtained by changing the matrix, i.e., from a martensitic to a stable austenitic matrix which can provide the requisite ductility and has the additional advantage of being work hardenable during service. In-service work hardening of the austenite matrix will be local to the surface and can provide additional wear resistance without sacrificing the component ductility that provides breakage resistance. The abrasion/erosion resistant wear alloy of the present invention is particularly suitable for use in high or low stress applications potentially exposed to impact loading. In contrast to stable austenite, it should be noted that retained, metastable austenite can be detrimental to wear alloy performance. Uncontrolled through-section transformation of the metastable austenite to martensite during service is undesirable because, a significant volume change occurs that can cause cracking.
Accordingly, one aspect of the present invention is drawn to an abrasion/erosion resistant wear alloy suitable for use in high or low stress applications potentially exposed to impact loading and having both good wear characteristics gained from a large volume of high carbide, together with a tough, stable austenitic matrix which provides requisite ductility and which has the additional advantage of being work hardenable during service, the alloy having a constituent composition consisting range essentially of:
æll~Q~
Case 5504 Constituent wt. Percent Carbon about 2.6 - 2.9 Manganese about 0.75 - 1.25 Silicon about 0.50 - 1.0 Nickel about 0.5 max. _ Chromium about 25 - 28 Molybdenum about 1.0 - 6.5 Copper about 0.5 max.
Phosphorous about <0.08 Sulfur about <0.05 with the balance essentially iron with the usual impurities.
Another aspect of the present invention is drawn to a particular composition for an abrasion/erosion resistant wear alloy of the type described above, the alloy having a particular constituent composition consisting essentially of:
Constituent Wt. Percent Carbon about 2.75 Manganese about l.oo Silicon about 0.75 Nickel about 0.2 Chromium about 27 Molybdenum about 6.25 Copper residual amounts Phosphorous residual amounts Sulfur residual amounts with the balance essentially iron with the usual impurities.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the present invention, its operating advantages Case 5504 . 2i~9 0 10 and specific results attained by its uses, reference is made to the accompanying drawings and the fo~llowing description in which preferred embodiments of the invention are disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
Fig. 1 is a drawing showing the austenite liquidus surface of the Fe-Cr-C system; and Fig. 2 is a drawing showing a corner of the metastable Fe-Cr-C liquidus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following discussion includes a description of the range and preferred compositions of the abrasion/erosion resistant wear alloy of the present invention. It is to be emphasized that this particular abrasion/erosion resistant wear alloy is suitable for use in high or low stress applications having potential exposure to impact loading. It provides both good wear characteristics gained from a large volume of high hardness carbides, and a tough, stable austenitic matrix which provide requisite ductility and which has the additional advantage of being work hardenable during service. The alloy has a composition consisting essentially of the following elements as set forth in the table below, the first column being the particular constituent, the second column being the preferred range in weight percent of these constituents, while the third column represents the preferred particular composition weight percents of these constituents.
Case 5504 21~91~
g Weiqht Percent Preferred Constituent Ranqe Composition Carbon about 2.6 - 2.9 about 2.75 Manganese about 0.75 - 1.25 about 1 00 - Silicon about 0.50 - 1.0 about 0.75 Nickel about 0.5 max. about 0.2 Chromium about 25 - 28 about 27 Molybdenum about 1.0 - 6.5 about 6.25 Copper about 0.5 max. residualamounts Phosphorous about <0.08 residualamounts Sulfur about <0.05 residualamounts The balance is essentially iron with the usual impurities.
In the above range and preferred compositions, the carbon is added to increased carbide volume and alloy hardness. The manganese is added to control cleanliness (i.e., scavenging embrittling elements such as sulfur). The silicon promotes castabilty while the chromium promotes carbide formation.
Finally, the molybdenum stabilizes the austenitic matrix and forms additional high hardness carbides.
The abrasion/erosion resistant wear alloy can be used as-cast. Alternatively, the alloy can be heat-treated or the composition can be changed within the range and coupled with other material processing can be made to develop an austenitic and/or martensitic structure tailored to a variety of wear conditions. For example, when erosive wear conditions predominate, a martensitic matrix may be preferable. Similarly, under more abrasive conditions, a more austenitic structure may be preferable.
It is preferred that the present invention be heat treated according to a two-step process, the first step during manufacture being an austenization step carried out in a temperature range of approximately 1750F to 1950F, the preferred temperaturè being approximately 1850F, for a Ca~e 5504 21~9~10 sufficient time to thoroughly homogenize the metallic structure throughout the parts being made. 'This step is important in obtaining a completely stable austenitic matrix.
The second step is a lower temperature tempering step S carried out in temperature range of approximately 5~F to 1000F, the preferred temperature being approximately 950F, again for a sufficient time to thoroughly homogenize the tempering effects throughout the parts being made.
Another important aspect of the chemical composition of the present invention is that the relative nominal levels of Manganese (Mn) and Silicon (Si) are maintained such that the weight percent of Mn is greater than the weight percent of Si, i.e., that a ratio of Mn/Si is greater than 1Ø This is important because the manganese addition offsets the loss of material toughness caused by the presence of silicon in the alloy. Whereas silicon is necessary to promote castability by improving liquid metal fluidity; some amount of brittleness is imparted to ferrous alloys by silicon additions.
The present invention provides large carbide volume fractions and high carbide hardness promoting good wear resistance. The austenitic matrix provides good resistance to cracking and breakage resistance and the added benefit of being able to be work hardened at the surface during service. This promotes wear resistance without impairing ductility. The abrasion/erosion resistance wear alloy of the present invention can be used to produce components having substantially longer service life, thereby reducing maintenance and replacement costs. Particular applications where the present abrasion/erosion resistant wear alloy can be used includes coal pulverizers or mineral crushing equipment wear surfaces for both abrasion and erosion-resistant applications It will be further appreciated that although the present abrasion/erosion resistant wear alloy is intended for use in coal grinding and pulverizing equipment, other erosive material handling systems and the like may benefit by employing this Case 5504 214~
alloy. It can also be used for other applications where wear resistance is needed. Examples would include shot blasting equipment, mining equipment, and slurry transport. Accordingly, while in accordance with provisions of the statutes there have been descri~ed herein specific embodiments of the inv~ntion, those skilled in the art will understand that nominal changes may be made in the form of the invention covered by the appended claims to enhance its use in various settings, and that all such modifications and improvements have been deleted herein for the sake of conciseness and readability but are properly within the scope of the following claims.
Claims (2)
1. An abrasion/erosion resistant wear alloy suitable for use in high or low stress applications having potential exposure to impact loading and having both good wear characteristics gained from a large volume of high hardness carbides and a tough, stable austenitic matrix, which provides requisite ductility and which has the additional advantage of being work-hardenable during service, the alloy having a constituent composition range consisting essentially of:
Constituent Wt. Percent Carbon about 2.6 - 2.9 Manganese about 0.75 - 1.25 Silicon about 0.50 - 1.0 Nickel about 0.5 max.
Chromium about 25 - 28 Molybdenum about 1.0 - 6.5 Copper about 0.5 max.
Phosphorous about <0.08 Sulfur about <0.05 with the balance essentially iron with the usual impurities.
Constituent Wt. Percent Carbon about 2.6 - 2.9 Manganese about 0.75 - 1.25 Silicon about 0.50 - 1.0 Nickel about 0.5 max.
Chromium about 25 - 28 Molybdenum about 1.0 - 6.5 Copper about 0.5 max.
Phosphorous about <0.08 Sulfur about <0.05 with the balance essentially iron with the usual impurities.
2. An abrasion/erosion resistant wear alloy suitable for use in high or low stress applications having potential exposure to impact loading and having both good wear characteristics gained from a large volume of high hardness carbides in a tough, stable austenitic matrix which provides requisite ductility and which has the additional advantage of being work hardenable during service, the alloy having a particular constituent composition consisting essentially of:
Constituent Wt. Percent Carbon about 2.75 Manganese about 1.00 Silicon about 0.75 Nickel about 0.2 Chromium about 27 Molybdenum about 6.25 Copper residual amounts Phosphorous residual amounts Sulfur residual amounts with the balance essentially iron with the usual impurities.
Constituent Wt. Percent Carbon about 2.75 Manganese about 1.00 Silicon about 0.75 Nickel about 0.2 Chromium about 27 Molybdenum about 6.25 Copper residual amounts Phosphorous residual amounts Sulfur residual amounts with the balance essentially iron with the usual impurities.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US23965994A | 1994-05-09 | 1994-05-09 | |
| US08/239,659 | 1994-05-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2149010A1 true CA2149010A1 (en) | 1995-11-10 |
Family
ID=22903157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2149010 Abandoned CA2149010A1 (en) | 1994-05-09 | 1995-05-09 | Abrasion/erosion resistant wear alloy |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2149010A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005078156A1 (en) * | 2004-02-16 | 2005-08-25 | Kevin Francis Dolman | Hardfacing ferroalloy materials |
-
1995
- 1995-05-09 CA CA 2149010 patent/CA2149010A1/en not_active Abandoned
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2005078156A1 (en) * | 2004-02-16 | 2005-08-25 | Kevin Francis Dolman | Hardfacing ferroalloy materials |
| EA009434B1 (en) * | 2004-02-16 | 2007-12-28 | Кевин Фрэнсис Долман | Hardfacing ferroalloy materials |
| AU2005212384B2 (en) * | 2004-02-16 | 2009-10-29 | Kevin Francis Dolman | Hardfacing ferroalloy materials |
| US8941032B2 (en) | 2004-02-16 | 2015-01-27 | Kevin Francis Dolman | Hardfacing ferroalloy materials |
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