KR20070015956A - Method for forming a hardened surface on a substrate - Google Patents

Abstract

The present invention includes a method of forming a metal coating. The metallic glass coating is formed on the metallic substrate. After formation of the coating, at least some of the metallic glass can be converted to a crystalline material having nanocrystalline particle size. The steps of this process are shown schematically in FIG. 1. Also included in the present invention are metal coatings comprising metal glass. In addition, the present invention includes a metal coating comprising a crystalline metal material, wherein at least a portion of the crystalline metal material has a nanocrystalline particle size.

Description

How to form a cured surface on a substrate {METHOD FOR FORMING A HARDENED SURFACE ON A SUBSTRATE}

Technical field

The present invention relates to metal coatings and methods of forming metal coatings.

Background of the Invention

Steel is a metal alloy commonly used in structures that require or benefit from strength because it can have exceptional strength properties. Steel can be used, for example, in building structures, tools, skeletal supports of engine parts, and protective shields of modern weapons.

The composition of the steel depends on the application of the alloy. In order to interpret the present application and claims below, "steel" does not contain more than 30% by weight of any other single element (except iron), the iron content is at least 55% by weight, and the carbon is at most 2 It is defined as an iron-based alloy that is limited to weight percent. In addition to iron, the steel alloy may incorporate manganese, nickel, chromium, molybdenum, and / or vanadium, for example. Steel alloys may also incorporate carbon, silicon, phosphorus and / or sulfur. However, if phosphorus, carbon, sulfur and silicon are present in amounts of several percent or more, they can be detrimental to overall steel quality. Thus, steel typically contains small amounts of phosphorus, carbon, sulfur and silicon. Steel includes a regular atomic arrangement, with periodic lamination arrangements forming a three-dimensional lattice defining the steel's internal structure. The internal structure (sometimes also called "microstructure") of traditional steel alloys is almost metallic and polycrystalline (which consists of many crystalline particles).

Steel is typically formed by cooling the molten alloy. The cooling rate will determine whether the alloy cools to form an internal structure that predominantly contains crystalline particles, or, in rare cases, a predominantly amorphous structure (so-called metal glass). In general, if cooling proceeds slowly (ie at a rate of less than about 10 ⁴ K / s), the particle size will increase and when cooling proceeds rapidly (ie at a rate of about 10 ⁴ K / s or more) It is observed that microcrystalline internal particle structures are formed, or in particular rare cases amorphous metal glass. The composition of a special molten alloy generally determines whether the alloy hardens as it forms to form microcrystalline grain structures or amorphous glass as the alloy cools rapidly. It is also noted that it has recently been discovered that special alloy compositions (not based on iron) can lead to microscopic particle formation, or metal glass formation, at relatively low cooling rates (such as 10 K / s). .

Both the microcrystalline particle internal structure and the metallic glass internal structure may have properties that are particularly desirable for applications for steel. In some applications, the amorphous nature of the metallic glass can provide desirable properties. For example, some glasses may have exceptionally high strength and hardness. In other applications, certain properties of the microcrystalline particle structure are preferred. Often, if the properties of the particle structure are preferred, these properties will be improved by reducing the particle size. For example, the preferred properties of microcrystalline particles (ie, particles having a size of about 10 ^-6 meters) are known as microcrystalline particle sizes of nanocrystalline particles (ie, particles having a size of about 10 ^-9 meters). It can often be improved by reducing it. It is generally more difficult to form particles of nanocrystalline particle size than to form particles of microcrystalline particle size. Therefore, it is desirable to develop improved methods for forming steel materials of nanocrystalline particle size. In addition, since it is often necessary to have a metallic glass structure, it is desirable to develop a method of forming metallic glass.

Summary of the Invention

In one aspect, the invention includes a method of forming a metal coating. The metallic glass coating is formed on the metallic substrate. After forming the coating, at least a portion of the metallic glass can be converted to a crystalline material having nanocrystalline particle size.

In another aspect, the present invention includes a metal coating comprising a metal glass.

In yet another aspect, the present invention includes a metal coating comprising a crystalline metal material, wherein at least a portion of the crystalline metal material has nanocrystalline particle size.

Brief description of the drawings

Preferred embodiments of the present invention are described below with reference to the following drawings.

1 is a block-diagram flowchart diagram of a method included in the present invention.

2 is a schematic perspective view of a barrel processed according to the method of the present invention.

3 is a fragmentary, schematic cross-sectional view of a metal material substrate in a pretreatment step included in the present invention.

4 is a view of the fragment of FIG. 3 shown in a processing step subsequent to the step of FIG.

5 is a view of the fragment of FIG. 3 shown in a processing step subsequent to that of FIG.

6 is a view of the fragment of FIG. 3 shown in a processing step subsequent to the step of FIG.

7 is an optical micrograph of a metal glass ribbon formed according to the method of the present invention, formed from a composition comprising Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ .

8 is a micrograph of a scanning electron microscope of a cross section of gas atomized powder particles formed according to the present invention, formed from a composition comprising Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ .

9 is a graph showing the results of a temperature difference analysis scan of a ribbon made in accordance with the present invention. The ribbon was made from a composition comprising Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ . The transition of the exothermic glass to crystallization occurs at 55O < 0 > C and the melting transition of the endothermic solid into a liquid occurs at 1,150 < 0 > C.

10 is a TEM micrograph of a steel alloy prepared according to the method of the present invention, which contains a composition of Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ , and was heat-treated at 65 ° C. for 1 hour. . Nanosized nanocomposite microstructures are visible to the naked eye and have a phase size of 1 to 75 nanometers.

11 shows Vickers hardness for different metal alloys. Specifically, FIG. 11 compares DARl (Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ ) and DAR20 (Fe ₆₄ Ti ₃ Cr ₅ Mo ₂ B ₁₆ C ₅ Si ₁ Al ₂ La ₂ ). Hardness is compared as a function of heat treatment temperature.

12 shows an example of a Vickers hardness test using a diamond pyramid indenter. Specifically, the upper part of the figure shows the test on the gas spray powder particles, and the lower part shows the test used on the melt spinning ribbon. The test composition was Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ It was.

FIG. 13 is an optical micrograph of a steel composition plasma sprayed onto a stainless steel substrate. FIG. The plasma-sprayed steel composition includes Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ . The upper part of Fig. 9 (a) is a cross sectional view of the sprayed material, and the lower part (b) shows the top surface of the coated material.

14 shows an x-ray diffraction scan of a plasma-sprayed deposit having a free surface. The plasma-sprayed composition was Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ .

FIG. 15 shows an x-ray diffraction scan of the plasma-sprayed composition of FIG. 14 and shows the structure at the substrate surface.

FIG. 16 shows a graph showing the coefficient of friction versus number of turns for a pin on disk test of a thermal spray coating. The coating tested was Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ . Note that while initial friction is low, Si ₃ N ₄ deposition and accumulation resulted in increased frictional forces. (The sliding friction coefficient for Si ₃ N ₄ itself is 0.8).

FIG. 17 is a profile curve of "wear-groove" on first-sprayed steel substrate after 2,000 cycles of pin on disk testing. As can be seen, instead of grooves developing over the steel substrate, Si ₃ N ₄ wears and deposits material onto the substrate. The composition tested was Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ .

Figure 18 _{(Fe 0 .8 CR 0 .2)} 81 B 17 W 2 of the first-a optical micrograph of the emitted ribbon. The alloy shows high ductility and can be bent vigorously without rupturing.

Figure 19 _{(Fe 0 .8 Cr 0 .2)} 75 B 17 Si 4 Al 4 data obtained from differential thermal analysis (upper graph) and _{Fe 63 Cr 8 Mo 2 B 17} C 5 Si 1 Al 4 ( bottom graph) Indicates. The graph curve shows the transition of the glass to crystalline and the melting temperature for the tested alloy.

20 shows peak crystallization temperatures measured by differential thermal analysis for various alloys. Specifically, Figure 20 is an alloy of _{Fe 63 Cr 8 Mo 2 B 17} C 5 Si 1 Al 4 to _{1, (Fe O .85 Cr 0} . L5) for ₁₇ to ₈₃ B _{2, (Fe 0 .8 Cr 0} . _{2) 83} to B ₁₇ to _{3, (Fe 0 .75 Cr 0} .25) to ₈₃ B ₁₇ to _{4, (Fe 0 .8 Mo 0} .2) with the _{83 B 17 5, (Fe 0} .6 Co 0 _.2 Cr _{0 .2) 83} to B ₁₇ to 6, (Fe _.8 Cr ₀ to _{0 .15 Mo 0 .05) 83 B} 17 as _{7, (Fe 0 .8 Cr 0} .2) 79 B 17 C 4 in the _{8, (Fe 0 .8 Cr 0} .2) 79 B 17 Si ₄ to the _{9, (Fe 0 .8 Cr 0} .2) 79 B 17 Al ₄ in a _{10, (Fe 0 .8 Cr 0} . _{2) 75} B ₁₇ Al ₄ C for ₄ to _{11, (Fe 0 .8 Cr 0} .2) 75 B 17 Si 4 C ₄ in the _{12, (Fe 0 .8 Cr 0} .2) 75 B 17 Si 4 Al ₄ to _{13, (Fe 0.8 Cr 0.2)} 71 B 17 Si 4 C 4 to Al ₄ to 14, (Fe Co _{0 .7 0 .1} Cr _{.2 0)} to ₈₃ B ₁₇ to 15, (Fe _{0 .8} Cr _{0 .2) 76} B ₁₇ Al ₇ a to _{16, (Fe 0 .8 Cr 0} .2) the ₇₉ B ₁₇ W ₂ C ₂ to _{17, (Fe 0 .8 Cr 0} .2) 81 B 17 W 2 in the _{18, (Fe 0 .8 Cr 0} .2) shows the ₈₀ B ₂₀ to 19.

21 shows the crystallization enthalpy measured by differential scanning for various alloys included in the present invention. Specifically, Figure 21 is an alloy _{Fe 63 Cr 8 Mo 2 B 17} C 5 Si ₁ Al of ₄ to 1, 2 to the _{(Fe 0.85 Cr 0.15) 83 B} 17, (Fe 0 .8 Cr 0 .2) 83 B ₁₇ to 3, the _{(Fe 0 .75 Cr 0 .25)} 83 B 17 to _{4, (Fe 0.8 Mo 0.2)} 83 to B ₁₇ to _{5, (Fe 0 .6 Co 0} .2 Cr 0 .2) 83 the B ₁₇ to _{6, (Fe 0 .8 Cr 0} . l5 Mo 0 .05) to a ₈₃ B ₁₇ 7, the _{(Fe 0. 8 Cr 0.2)} 79 B 17 C 4 to 8, (Fe _{0 .8} Cr _{0. 2) 79} to B ₁₇ Si ₄ to 9, (Fe _.8 Cr _{0 0 2) 79} B ₁₇ Al ₄ to 10, (as _{Fe 0.8 Cr 0.2) 75 B 17} Al 4 C ₄ to 11, ( Fe _.8 Cr ₀ to _{0 .2) 75 B 17 Si 4} C 4 to 12, (Fe _.8 Cr ₀ to _{0 .2) 75} B ₁₇ Si ₄ the _{Al 4 13, (Fe 0 .8} Cr O .2 ) ₇₁ B ₁₇ Si ₄ C ₄ to Al ₄ to 14, (Fe Co _{0 .7 0 .1} Cr _{.2 0)} in a _{83 B 17 15, (Fe 0} .8 Cr 0 .2) 76 B 17 Al 7 in the _{16, (Fe 0 .8 Cr 0} .2) 79 B 17 with the W ₂ C ₂ 17, as _{(Fe 0 .8 Cr 0 .2)} 81 B 17 W 2 to 18, (Fe _{0 .8} Cr _{0. 2)} shows the ₈₀ B ₂₀ to 19.

FIG. 22 shows a graph of strain rate into crystallization strain of glass for various alloys included in the present invention. FIG. Specifically, Figure 22 is an alloy _{Fe 63 Cr 8 Mo 2 B 17} C 5 Si 1 Al 4 a _{1, (Fe 0 .85 Cr 0} .15) 83 B 17 as a _{2, (Fe 0 .8 Cr O} . _{2) 83} to B ₁₇ as _{3, (Fe 0 .75 Cr 0} .25) as the ₈₃ B _{17 4, (Fe 0 .8 Mo 0} .2) as a _{83 B 17 5, (Fe 0} .6 Co 0 _.2 Cr _{0 .2) 83} to B ₁₇ 6 _{a, (Fe 0 .8 Cr 0.} 15 Mo 0.05) 83 B 17 a as _{7, (Fe 0 .8 Cr 0} .2) the ₇₉ B ₁₇ C ₄ 8 _{a, (Fe 0 .8 Cr 0 .2} ) 79 B ₁₇ Si ₄ a as _{9, (Fe 0.8 Cr 0.2)} 79 B 17 Al ₄ a as _{10, (Fe 0 .8 Cr 0} .2) 75 B 17 Al _4, a C ₄ as _{11, (Fe 0 .8 Cr 0} .2) 75 B 17 Si 4 C 4 for a _{12, (Fe 0 .8 Cr 0} .2) a ₇₅ B ₁₇ Si ₄ Al ₄ to 13, ( _{Fe 0 .8 Cr 0 .2) 71} B 17 Si 4 C 4 to Al ₄ as _{14, (Fe 0.7 Co 0.1 Cr} O.2) 83 B 17 a as _{15, (Fe 0 .8 Cr 0} .2) 76 ₇ as the B ₁₇ Al _{16, (Fe 0 .8 Cr 0} .2) 79 B 17 W ₂ C ₂ as the _{17, (Fe 0 .8 Cr 0} .2) 81 B ₁₇ W ₂ as the 18, (Fe _{0 .8} Cr _{0 .2)} shows a B _{80 20} 19 a.

FIG. 23 shows peak melting temperatures measured by differential pyrolysis for various alloys included in the present invention. FIG. Specifically, Figure 23 is an alloy _{Fe 63 Cr 8 Mo 2 B 17} C 5 Si 1 Al 4 to 1, the _{(Fe 0 .85 Cr 0 .15)} 83 B 17 to _{2, (Fe 0 .8 Cr 0} . _{2) 83} to B ₁₇ to _{3, (Fe 0 .75 Cr 0} .25) to ₈₃ B ₁₇ to _{4, (Fe 0.8 Mo 0.2)} 83 to B ₁₇ to _{5, (Fe 0 .6 Co 0} .2 Cr 0 _{2) 83} to B ₁₇ to 6, (Fe _.8 Cr ₀ to _{0 .15 Mo 0 .05) 83 B} 17 as _{7, (Fe 0.8 Cr 0.2)} 79 B ₁₇ C for ₄ to 8, (Fe _0. the _{8 Cr 0 .2) 79 B 17} Si 4 to 9, (Fe _{0 .8} Cr _{.2 O)} a ₇₉ B ₁₇ Al ₄ to 10, the _{(Fe 0.8 Cr 0.2) 75 B} 17 Al 4 C 4 to 11 _{, (Fe 0 .8 Cr 0 .2} ) 75 B 17 Si 4 C ₄ in the _{12, (Fe 0 .8 Cr 0} .2) 75 B 17 Si 4 Al ₄ in a 13, (Fe _{0 .8} Cr _{0 .2) 71 B 17 Si 4 C} 4 to Al ₄ to 14, (Fe Co _{0 .7 0 .1} Cr _{.2 0)} to ₈₃ B ₁₇ to _{15, (Fe 0 .8 Cr 0} .2) 76 B 17 the Al ₇ to _{16, (Fe 0 .8 Cr 0} .2) 79 B 17 with the _{W 2 C 2 17, (Fe} 0 .8 Cr 0 .2) 81 B ₁₇ W ₂ in the 18, (Fe _{0. 8} Cr _{0 .2)} it shows the ₈₀ B ₂₀ to 19.

Detailed description of the invention

The invention also includes methods for forming steel materials having composite microstructures of nanocrystalline size, methods of using such steel materials, and steel material compositions. Methods encompassed by the present invention are generally described with reference to the block diagram of FIG. 1. In the first step (A) a molten alloy is formed. Such alloys include steel compositions. Representative alloys include at least 50% Fe and Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, At least one element selected from the group consisting of Tm, Yb, and Lu; And at least one element selected from the group consisting of B, C, N, O, P and S. In a particular aspect of the invention, the alloy will be a magnetic alloy having ultrafine crystal grains having a composition represented by the following formula: Fe (100-xy) M (x) B (y) (atomic percent) where M is At least one element selected from Ti, Zr, Hf, V, Nb, Mo, Ta, Cr, W and Mn, wherein 15≥x≥4, 25≥y≥2, and 35≥ (x + y) ≥ 7. In addition, at least 50% of the alloy structure is preferably occupied by crystal grains having an average size of 100 kPa or less, the crystal grains being based on the bcc structure. The alloy may further contain X (Si, Ge, P, Ga, etc.) and / or T (Au, Co, Ni, etc.).

The alloy of the present invention preferably contains less than 11 elements, more preferably less than 7 elements. In addition, the alloy may include less than five elements. The advantage of having fewer elements in the composition is that if fewer components are used to form the material, it may be easier to reproduce the material. In general, the alloy of the present invention has 4 to 6 elements in the composition. Among these elements iron; Chromium which can be included for corrosion resistance; Boron and / or phosphorus, which may be included to produce a specific glass transition temperature; And one or both of molybdenum and tungsten, which may be included for hardness. Exemplary alloys that can be used in the method of the present invention are as _{follows: (Fe 0.85 Cr 0.15) 83} B 17, (Fe 0 .8 Cr 0 .2) 83 B 17, (Fe 0 .75 Cr 0 .25) _{83 B 17, (Fe 0 .8} Mo 0 .2) 83 B 17, (Fe 0.6 Co 0.2 Cr 0.2) 83 B 17, (Fe 0 .8 Cr 0 .15 Mo 0 .05) 83 B 17, (Fe _{0 .8 Cr 0 .2) 79 B} 17 C 4, (Fe 0 .8 Cr 0 .2) 79 B 17 Si 4, (Fe 0.8 Cr 0.2) 79 B 17 Al 4, (Fe 0 .8 Cr 0. _{2) 75 B 17 Al 4 C} 4, (Fe 0 .8 Cr 0 .2) 75 B 17 Si 4 C 4, (Fe 0 .8 Cr 0 .2) 75 B 17 Si 4 Al 4, (Fe 0.8 Cr _{0.2) 71 B 17 Si 4 C} 4 Al 4, (Fe 0 .7 Co 0 .1 Cr 0 .2) 83 B 17, (Fe 0 .8 Cr 0 .2) 76 B 17 Al 7, (Fe 0. _{8 Cr 0 .2) 79 B 17} W 2 C 2, (Fe 0.8 Cr 0.2) 81 B 17 W 2, and _{(Fe 0 .8 Cr 0 .2)} 80 B 20.

The alloy of step (A) can be formed, for example, by melting the composition under an argon atmosphere.

In step (B) of FIG. 1, the alloy is cooled to form a metallic glass. Such cooling typically includes a rate of at least about 10 ⁴ K / s, which rate depends on the particular composition of the molten alloy. Cooling can be accomplished by a number of different treatments including, for example, melt-spinning, gas spraying, centrifugal spraying, water spraying, and melt quenching. The fine powder can be hardened by, for example, hipping, hot compression, hot extrusion, powder rolling, powder forging and compaction. In an exemplary method, the cooling of step (B) is by centrifugal spraying. Preferably, the melt stream remains in the centrifugal cup and is hit by high pressure helium gas to promote rapid cooling (10 ⁵ K / s or more). Helium gas can be collected, purified and reused. The speed of the rotating centrifugal cup is preferably about 40,000 RPM, which can be adjusted to produce a fine powder having an average size of about 25 micrometers.

Referring to step (C) of FIG. 1, the metal glass of step (B) is devitrified to form a crystalline steel material having nanocrystalline particle size. Such devitrification can be accomplished by heating to a temperature from about 600 ° C. to below the melting temperature of the alloy. This heating allows for a phase change in the solid state, where the amorphous phase of the metallic glass is converted into one or more crystalline solid phases. Solid state devitrification of the amorphous precursor from step (B) allows uniform nucleation to occur throughout the metal glass to form nanocrystalline particles inside the glass. The metal matrix microstructures formed through devitrification may comprise a steel matrix (iron with decomposed gaps) having a mixture of closely bonded ceramic precipitates (transition metal carbides, borides, silicides, etc.). The nanocrystalline-sized metal matrix composite particle structure allows for a combination of improved mechanical properties over larger particle sizes or properties that will be present with metallic glass. Such improved mechanical properties can be, for example, high strength combined with significant ductility, and high hardness.

The specific temperature used to de-vitrify the metallic glass may depend on the particular alloy used for the glass and the specific application time. Post-treatment of the metallized material which has been liberated from step (C) may include a surface treatment used to transform only the surface of the material into metallic glass. Representative surface treatment techniques include high and low pressure plasma spraying, high speed flame spraying, and thermal spraying. Plasma spraying can be accomplished using a plasma spray system. Post-treatment can provide improvements in terms of, for example, corrosion resistance and lowering the coefficient of friction of steel materials. Thus, it may be advantageous to treat at least the surface of the crystalline steel material to convert such surface to metallic glass. Metal glass coatings are also advantageous over existing coatings such as chromium, nickel and tin plating in that metal glass coatings are relatively cheaper and can provide better metallurgical bonds between the surface and the base metal. Note that it can provide.

2, a particular specific application of the present invention is shown. Specifically, FIG. 2 shows a metal barrel 50 sprayed with molten metal material 52. The molten metal material 52 is sprayed from the spray device 54 and may comprise, for example, one or more of the representative alloys of the present invention described above. Molten metal can be formed by melting the alloy composition under an argon atmosphere and subsequently spraying the alloy composition centrifugally. When the melt stream remains in the centrifugal cup, the melt stream is struck by high pressure helium gas to form a fine powder of solidified metal alloy material, which has a mean size of about 25 micrometers. The fine powder can be supplied to a plasma (high or low pressure) system, where the fine powder is converted to a liquid spray that is sprayed on the inside and outside of the metal drum 50. In certain applications, the drum 50 includes a steel drum, such as, for example, a 55 gallon steel drum. Note that the powder may or may not melt completely when exposed to the plasma, and will be deposited on and on the surface of the barrel 50 as a continuous coating. In any case, the thermally sprayed metallic material 52 inside and on the drum 50 cools rapidly to form metallic glass. The drum 50 may subsequently be heat treated at a temperature of at least 600 ° C. to cause the glass to be devitrified.

Metal structures formed on and within barrel 50 from material 52 may have greater corrosion resistance than stainless steel. The drum 50 is used for strong corrosive materials or hazardous materials such as, for example, waste nuclear fuel. If the surface of the material 52 is coated with metallic glass, anti-corrosive properties and low coefficient of friction properties associated with the metallic glass can be obtained.

3-6 illustrate another specific application of the present invention. 3, a metal substrate 100 is provided. Such substrates may include, for example, one or more of the above-described exemplary alloys of the present invention.

4, the metal melt 102 is sprayed onto the substrate 100 using a sprayer 104. Melt 102 is, for _{example, (Fe 0 .85 Cr 0 .15} ) 83 B 17, (Fe 0 .8 Cr 0 .2) 83 B 17, (Fe 0.75 Cr 0.25) 83 B 17, (Fe 0 _{.8 Mo 0 .2) 83 B 17} , (Fe 0 .6 Co 0 .2 Cr 0 .2) 83 B 17, (Fe 0 .8 Cr 0 .15 Mo 0. O5) 83 B 17, (Fe 0.8 _{Cr 0.2) 79 B 17 C 4} , (Fe 0 .8 Cr 0 .2) 79 B 17 Si 4, (Fe 0 .8 Cr 0 .2) 79 B 17 A1 4, (Fe 0 .8 Cr 0 .2 _{) 75 B 17 Al 4 C 4} , (Fe 0 .8 Cr 0 .2) 75 B 17 Si 4 C 4, (Fe 0 .8 Cr 0 .2) 75 B 17 Si 4 Al 4, (Fe 0.8 Cr 0.2 _{) 71 B 17 Si 4 C 4} Al 4, (Fe 0 .7 Co O .1 Cr 0 .2) 83 B 17, (Fe 0 .8 Cr 0 .2) 76 B 17 Al 7, (Fe 0 .8 _{Cr 0 .2) 79 B 17 W} 2 C 2, (Fe 0.8 Cr 0.2) 81 B 17 W 2, and (comprise a molten alloy comprising at least one of Fe Cr _{O.8 O.2) 80} B _2O Can be. Instead of being in molten form, material 102 may alternatively comprise a powder material heated to a temperature sufficient to bond with metal layer 100.

Material 102 is deposited over substrate 100 to form layer 106. Material 102 also heats the exposed surface of material 100 to form a heat treated portion 108 of material 100. If the material 100 comprises a metallic glass, the heat treated portion 108 may comprise a deglassed material. Specifically, if layer 106 is formed at a temperature that heats the surface of layer 100 to a temperature greater than 600 ° C., this heating may cause a portion of the material 100 exposed to that temperature to be devitrified. . In certain applications, temperatures greater than 600 ° C. may be entirely transmitted through the substrate to heat treat the entire thickness of material 100. The thermal spray nozzle 104 is resistant to the temperature and composition of the material 102.

5, the substrate 100 is shown after the layer 106 is formed over the entire surface of the substrate 100. The heat treated portion 108 also extends over the entire surface of the substrate 100. In certain embodiments, layer 106 may be formed as a metallic glass.

Referring to FIG. 6, subsequent processing of the type shown in FIG. 4 may be used to form a plurality of heat treated layers 120 and exposed outer surface layers 124. Note that one of the bottom heat treated layers 120 is the previous layer 106. Subsequent formation of another metal glass layer over layer 106 heat treated the entirety of layer 106. In certain embodiments in which layer 106 comprises a metallic glass, this heat treatment can de-vitrify layer 106. Thus, the heat treated layer 120 may include a deglassed metal layer. In an alternative method of the present invention, each of layers 106 and 120 may be deposited as a metal glass, and may remain in metal glass form while depositing the remaining layer 120. At this time, if necessary, some or all of the deposited layers may be heat treated to at least partially de-vitrify the coating defined by layers 106 and 120.

The outermost layer 124 may or may not be heat treated and may comprise metallic glass. Thus, the method of the present invention may allow an outer coating to be formed over layer 100, which includes an outermost layer of deglassed metal layer 120 and metal glass 124. The method described with reference to FIGS. 3-6 can be applied to numerous uses, including military use. In detail, the armor may be formed of the material 100. If the armor is punctured or ruptured, the method of FIGS. 3-6 may be used to repair the armor and effectively make the metal shell over the weakened portion of the armor. The thermal spray device 104 may be modified to be useful in war situations.

In addition to the use described above with regard to the materials of the present invention, the materials can be used as powders for surface finishes (ie mechanical blasting) and surface treatments such as, for example, shot peening.

The present invention can be regarded as a method for forming a new group of steels called de-vitrified nanocomposite (DNC) steels, which DNC steels are expressed by treating the steel through solid-solid deformation (specifically, glass de-vitrification). Nanoscale (less than 100 nanometers) microstructured particle size. Alloys with low cooling rates (less than 10 ⁶ K / s) have been developed for the formation of metallic glass, so that the alloy can be cooled or cooled (eg, melt-spinning, melt quenching, etc.) or sprayed (gas, water, When rapidly hardened by a method such as centrifugation, the alloy composition forms metal glass. Glass is used as the precursor stage and the alloy is subsequently processed through glass de-vitrification strain when heated above the crystallization temperature of the alloy. Due to the uniform nucleation in the glass, coupled with the high nucleation frequency, there is little time for particle growth to proceed, resulting in nanoscale nanocomposite microstructures (ie particles). Nanocomposite microstructures can result in materials with significantly increased hardness and strength compared to traditional steel alloys.

Early studies described herein showed that DNC steels formed in accordance with the methods of the present invention have exceptional hardness and wear resistance and could potentially be used for applications involving sliding, rolling or rotation. In addition, initial studies have shown that unlubricated DNC steel surfaces have an exceptionally low coefficient of friction (in the lubricated steel range), which can be beneficial properties to reduce wear resistance, frictional energy loss, and heat between moving surfaces. gave. This makes it possible to use DNC steel in non-lubricated applications and may also be useful as an anti-rupture mechanism that allows additional time before bursting in some applications, such as gasoline or diesel engines, where the lubricity is unexpectedly lost. The high wear resistance of DNC steel, combined with low friction, may allow for extended life of parts formed from DNC steel as compared to parts formed from traditional steel alloys. This may allow for significant savings in operating energy and costs associated with component replacement, repair, maintenance and downtime. Typical applications using the DNC steel of the present invention include bearings, barrel surfaces, shock bearing journals, hydraulic cylinder connecting rods, crankshafts, pistons, cylinder liners, gears, camshafts, universal joints, valves, gun breach boxes, missile launch tubes. , And tank gearbox.

Unlike traditional steel alloys, which rely on the manipulation of solid eutectic strains (γ _sol = α _sol + Fe ₃ C), DNC steels use a different approach, specifically through the glass de-vitrification strain in solid / solid state. Use processing. DNC steel alloys with exceptionally low cooling rates (10 ³ K / s to 10 ⁵ K / s) have been developed for metal glass formation. This enables the creation of metallic glass structures during rapid solidification via cold surfaces or spray methods.

Examples of DNC steel melt spinning ribbons and gas atomized powders are shown in FIGS. 7 and 8, respectively. Metallic glass structures are produced by all of these rapid solidification treatments. The glass precursor may be devitrized into the microstructure of the nanoscale composite by heating above the crystallization temperature.

A differential pyrolysis scan for the first-spun DNC steel is in FIG. 9. The glass crystallization temperature for the alloys included in the present invention typically varies from 750K to 900K, the modified enthalpy is from -75 J / g to -200 J / g, and the melting temperature is from 1,375K to l, 500K (Figure 20). As described in the chart of -23). Because of the uniform nucleation and extremely high nucleation frequencies present during the crystallization of the alloy of the present invention, there may be little time for the particles to grow before they collide between neighboring particles and, therefore, nanoscale nanocomposite micros The structure is formed. Individual phase sizes can vary from 1 to 75 nanometers, which is finer than traditional steel produced by traditional casting or even steel produced when rapidly solidified. When the microstructure is reduced to nanoscale levels, a high percentage of atoms in the material (about 30%) can be related to particle boundaries, and extremely high density of two-dimensional defect boundaries (such as phases at particle boundaries). Is in the microstructure. The microstructure of the devitrified ribbon showing the nanoscale nanocomposite microstructures is shown in FIG. 10. Nanostructures lead to the development of ultimate strength and hardness, which is significantly higher than those found in traditional steel or other metal based alloys.

The hardness of the glass and de-vitrified DNC steels was measured using both nanoindenter and Vickers microhardness tests, and a good match is found between the two methods. Berkovich indenter is used for gas sprayed particles from first-spun and heat-treated sieved (10-20 micrometers and 75-100 micrometers), Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ alloy Specialized nanoindenter tests were performed as a function of depth into the particles. The modulus of elasticity was observed to be as high as 300 GPa, which is about 50% higher than traditional steel (traditional steel typically exhibits modulus of elasticity of 200 GPa to 220 GPa). This can be a beneficial result of increasing bond strength, because it allows for little tolerance to be maintained while high elastic loads are applied and may have additional advantages with regard to wear resistance. Hardness was also observed to be extremely high, greater than 15 GPa, which is harder than traditional metallic materials. Examples of various compositions that can be used in the methods of the present invention to form rigid materials are shown in Table 1. In the table, reference is given to various compositions to simplify the reference to the compositions herein (specifically, these compositions are referred to as alloy DARX). Table 2 contrasts the hardness of various materials with alloy DAR1.

TABLE 1

TABLE 2

From the hardness measured for DAR1, the strength obtained for DNC steel can be estimated to be 725 ksi, which is much higher than traditional steel (150 ksi) or ultra high strength (220 ksi) steel. If plasticity is fully expressed, the strength obtained can be estimated to be one third of the hardness. This gives the DNC steel a specific strength of 0.65 x 10 ⁶ M, which makes this material a substitute for Al in lightweight applications. Little difference in hardness was found between large and small heated powders, meaning that similar microstructures were obtained regardless of powder size. Note that the hardness test described herein relates to the material DAR1 (Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ ) which is not a preferred material of the present invention. Rather, preferred materials of the present invention have fewer elements, which are listed in Table 1 as DAR2 to DAR 19.

In FIG. 11 a preferred substance of the invention (specifically DAR20) is compared with DAR1. Specifically, Vickers microhardness measurements using a 100 gram load on the first-sprayed alloy were performed for powder size classifications from 75 micrometers to 100 micrometers and also as a function of heat treatment temperature. The alloys tested showed extreme hardness from 10.1 GPa to 16.0 GPa Vickers hardness. An example of diamond pyramidal indentation for melt spinning ribbon and gas-spray powder particles is shown in FIG. 12. Rockwell C is the most common hardness measure for steel, but in this case it cannot be used due to the extreme hardness of the inventive alloys (out of Rockwell C criteria). Note that the Vickers hardness values of 9.2 GPa correspond to Rockwell C of 68. Referring again to FIG. 11, note that in the first-sprayed alloy of the present invention little change in hardness occurs after subsequent heat treatment. This may be important, because this means that the optimum microstructure is obtained immediately during solidification, which means that the optimum structure is stable against high temperatures (at least up to 85 ° C., as shown in FIG. 11).

DNC steel contains a combination of a plurality of elements, which results in a relatively low melting point (typically around 1,150 ° C.) and low melt viscosity. This can make it easy to process the DNC steel from the liquid state and from the ideal feedstock material to form a coating by thermal evaporation. The first low plasma spray test was performed using a sprayed 20 to 50 micron Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ steel powder as feed stock. Several uniform DNC steel coatings of 0.1 inch thickness were deposited on 4 "x4" 301 stainless steel plates (Figure 13). Typical thermal evaporation coatings are only 25 micrometers to 100 micrometers thick, but much thicker coatings (up to 2,500 micrometers) have been sprayed (i.e. thinner coatings for spraying are easier to describe in extreme cases, Thicker coatings were sprayed to illustrate the workability of the method of the invention).

Metallographic examinations of the coatings indicated that the percent porosity of the original coating was at least 3%. An X-ray diffraction scan was performed on both the substrate side of the coating and the free surface side of the coating, covering the entire cross section of the coating. Shows that an amorphous structure has been obtained (specifically, FIG. 14 shows the x-ray structure of the free surface side of the coating and FIG. 15 shows the x-ray structure of the substrate side of the coating). Differential scanning calorimetry demonstrated the formation of glass structures showing high crystallization enthalpy (-110 J / g) in the coating. This result is surprising because of the fact that the substrate and the maximum thickness of the coating resulting from the continuous accumulation of a continuous layer of deposited powder have not cooled. Therefore, DNC steel coatings represent a group of materials called bulk glass. Bulk glass is generally very difficult to manufacture, but is easily formed by heat treatment in DNC alloys.

First-sprayed DNC metal glass coatings can be deglassized into nanoscale structures by heating above the crystallization temperature. However, due to the unique properties of metallic glass, the glass state itself can be useful as a coating. Metallic glass is essentially a super-cooled liquid and has a very homogeneous structure. Typically there are few defects and there may be no particle and phase boundaries completely. Hardness tests were performed on both first-sprayed (amorphous) and heat-treated (for 1 hour at 800 ° C.) nanocrystalline coatings. Vickers hardness of these coatings was observed to be 10.9 GPa and 13.8 GPa for the first-sprayed and heat treated coatings, respectively. It should be noted that the amorphous sample is not as hard as the crystalline sample, but is still harder than the hardest tool steel (about 9.3 GPa), or tungsten carbon (WC) cemented carbide cutting tool (about 10.0 GPa).

Tribological test experiments were performed using the ASTM G99 pin-on-disk test for the first-sprayed and heat-treated (1 hour at 100 ° C.) plasma sprayed coatings. The "pin" was a 1/2 inch diameter Si ₃ N ₄ ball, which was rotated at a test speed of 97 RPM without lubrication at all with a test radius of 10.4 mm. During the test, the coefficient of friction was measured (Figure 16). The static friction coefficient for the steel substrate was both 0.22 at both the first-sprayed and heat treated conditions, indicating a low value. For example, the following sliding coefficients of friction were obtained for species sliding over normalized steel (0.13% C, 3.42% Ni): aluminum (0.6), weak brass (0.5), copper (0.8), Cast iron (0.4), and normalized steel (0.8 by itself). For traditional steels, the coefficient of static friction for unlubricated surfaces generally varies from 0.8 to 1.0, while lubricated steels have much lower values (typically 0.1 to 0.25). Therefore, unlubricated DNC steels have a static friction coefficient within the lubricated steel surface range. Thus, the use of DNC steel coatings in place of traditional steels can eliminate lubrication in some applications. Note that the sliding friction coefficient of the steel substrate cannot be measured due to the Si ₃ N ₄ deposition from the fins.

The profile of the wear surface of the steel showed that the steel did not wear at all during the test (FIG. 17). Instead of the expected wear grooves, raised hills of deposited Si ₃ N ₄ were found on the steel surface. Testing of silicon nitride balls showed that they suffered large ball wear traces as a result of wear. This was surprising because of the hardness of the ball material (15.4 GPa), because it was specially used for this type of test due to its excessive hardness and wear resistance. Note that Si ₃ N ₄ is the hardest fin material currently available to perform this ASTM test.

The Fe ₆₃ Cr ₈ Mo ₂ B ₁₇ C ₅ Si ₁ Al ₄ steel used to generate the data described above is a representative DNC steel. However, this steel has the disadvantage of including numerous elements inside the steel, which can make it difficult to produce a uniform batch of materials. Thus, improved DNC alloys have been developed. These improved alloys are listed in Table 1 as DAR2 to DAR19. The alloy is designed to form metallic glass at low cooling rates and is also designed to reduce the number of elements used in the alloy.

The ingots of the 19 alloys listed in Table 1 were melt spun at 15 m / s with the following melt-spinning parameters: chamber of 1/3 atmospheric helium, discharge pressure of 150 Torr, emission temperature of 1,400 ° C, wheels up to 6 mm Crucibles at distance, and crucibles at 0.81 mm to 0.84 mm orifice diameter.

All of the tested alloys were melt spun with almost no problem. Interestingly, many preferred alloys (ie, DAR2 to DAR19) formed uniform continuous ribbons up to 10 meters long. This may be due to increased glass forming capacity and increased ductility of the glass produced in relation to the less desirable alloy DAR1. The quality of the ribbon was checked by bending the ribbon back and forth until it broke, indicating that alloys DAR2 to DAR19 all had higher ductility than the DAR1 alloy. Indeed, some of the alloys DAR2 to DAR19 in the form of ribbons were not broken by bending and had to be cut. An example of a molten spinning ribbon showing high ductility is shown in FIG. 18, which was formed from the material DAR18 (Fe _0.8 Cr _0.2 ) ₈₁ B ₁₇ W ₂ .

Differential thermal analysis (DTA) and differential calorimetry (DSC) studies were performed for each melt spun ribbon sample at a heating rate of 10 ° C./min at high purity argon between 30 ° C. and 1,375 ° C. _{DAR14 ((Fe 0 .8 Cr 0} .2) 75 B 17 Si 4 Al 4) and _{DAR1 (Fe 63 Cr 8 Mo 2} B 17 C 5 Si 1 Al 4) a typical DTA scan showing the comparison shown in Fig. 19 in do. From this DTA / DSC study, the strain temperature, strain enthalpy, strain rate, and melting temperature of the glass into crystalline were measured. The results of this study are shown in FIGS. 20-23. As can be seen, all alloys except one (specifically, DAR5 ((Fe _0.8 Mo _0.2 ) ₈₃ B ₁₇ ), formed metal glass structures upon melt-spinning at reduced cooling rates. Therefore, the alloys were sprayed When formed, it is expected to form a metallic glass powder.

Vickers hardness test using a 100 gram load was performed on the melt spun ribbon cross section of each alloy in the first-spun and heat treated (1 hour at 700 ° C. and 1 hour at 800 ° C.) conditions. To get a recordable average value, 10 Vickers hardness tests were performed on each of the five ribbons for each sample (60 samples in total). In general, only small hardness changes were found when the same sample was tested. A summary of the completed Vickers hardness measurements is shown in Table 4.

TABLE 4

As represented by the tables and figures provided herein, the materials of the present invention having less than 11 elements, more preferably less than 7 elements, may form glass compositions. It is not easy to form a material having such a limited number of elements, and they can also form metallic glass. However, this has been achieved in the present invention. The present invention has also developed an improved ductile and tough DNC steel alloy, which maintains or even improves hardness. DNC alloys are thought to be useful in a number of sectors, including military applications, because of their strength and wear resistance. The alloy can also be resistant to electrochemical attack (ie, corrosion). In general, as the size of microstructures decreases, the electrochemical resistance of particular materials is expected to increase. Therefore, nanocrystalline sized DNC microstructures are expected to have good corrosion resistance. In addition, metal glass DNC structures can have improved corrosion resistance due to the high uniformity (short ranges on the order of 2 nanometers length scale) and the absence of two-dimensional defects (such as particle or phase boundaries). Specifically, the same single-phase structure can make the site difficult to initialize for anionic attack and electron transfer because there will be no distinct cathode and anode sites. Although metal glass or nanostructures of certain compositions may have higher relative resistance to electrochemical attack than the same material in bulk form, the material's nobility will depend on both structure and composition. For example, high levels of chromium can improve resistance to electrochemical attack.

An advantage of the alloys described herein is that these alloys can have a relatively simple composition (ie, 4 to 6 elements). In addition, the alloy may contain a relatively high percentage of transition metals (90% to 97%), which may result in improved industrial properties of the material.

The distinction of the materials of the present invention over traditional hard materials is that the materials of the present invention do not contain carbon at all. In traditional steels, hardness is typically directly related to the carbon content in martensite. In contrast, the extreme hardness of DNC steels results from the development of nanoscale nanocomposite microstructures rather than from martensite deformation. The advantage of the carbon-free composition is that extremely hard alloys can still be developed to be of moderate ductility, which is typically not possible with traditional steel alloys (ie, mitten martensite and transition metal carbides are typically hard, Is also brittle).

In particular, Group VI transition metals (Cr, Mo, and W) may be added to the DNC steel. Consistent with data for traditional steel alloys, chromium is also expected to provide excellent corrosion resistance. Exceptionally, molybdenum and tungsten may also be added to enhance the hardness of the DNC steel. Tungsten can also increase or increase ductility while increasing hardness.

Due to the hardness and high strength (greater than 725 ksi) of DNC steel, DNC steel can be difficult to process into bulk parts starting from powder and using traditional powder metallurgical solidification treatment. However, DNC steel can be easy to process from the liquid state. Alternatively, the powder of DNC steel can be supplied through a traditional plasma gun and can be sprayed as a coating on a metal substrate with good adhesion and no cracking. Other methods of forming a coating of DNC steel include axial feed plasma spray, traditional plasma spray, high speed flame spray, and explosion spray.

When DNC steel is thermally sprayed onto a metal substrate, the metal glass structure can be easily formed. If continuous layers are continuously sprayed on the bulk substrate (thickness greater than 0.1 inch), metal glass can be formed. This is probably the cheapest and easiest way to form metallic glass coatings or even bulk glass monolithic parts.

DNC steels can rapidly solidify into amorphous glass precursors, and then the rapidly solidified powders can solidify into useful forms. Therefore, the technical cost of the present invention can be related to three items: alloy cost, powder production cost, and solidification cost. All three items can be estimated. In order to produce rapidly solidified powders, centrifugal spraying may be the best method despite relatively low production rates. If it is convenient to prepare the DNC steel powder by water spraying, the processing cost of preparing the powder can drop by a few pennies per pound. Powder solidification costs will depend on the particular application and the thickness of the coating. Coatings between 5 micrometers and 2,500 micrometers thick can be readily deposited using traditional commercially available thermal evaporation methods such as plasma spraying or high speed flame spraying. The cost of DNC steel can be advantageously compared for other hard materials such as, for example, diamond and cubic BN. DNC steel coatings can also be a direct competitive technique to replace tungsten carbide cemented carbide coatings, because DNC steels exhibit higher hardness and greater tensile ductility.

Although the present invention has been described with respect to the coated steel alloy compositions of the present invention on metal substrates, the alloys of the present invention may also provide a hard and / or smooth surface over a non-metal substrate, for example, such as ceramics. It should be understood that the coating may be on a non-metal substrate.

Claims (13)

Providing a substrate; And A method of forming a cured surface on a substrate comprising forming a molten alloy and cooling the alloy to form a metallic glass coating over the substrate, the method comprising: Said molten alloy forming step comprises forming a continuous accumulation of a continuous metal glass layer, said metal glass coating having a hardness of at least about 9.2 GPa, at least one element selected from the group comprising iron and chromium, A method of forming a cured surface comprising an alloy containing one or both of at least one element selected from the group containing boron and phosphorus, molybdenum and tungsten. Providing a substrate; At least one element selected from the group containing boron and phosphorus, having a first hardness of at least 9.2 GPa on the substrate and cooling the alloy to form a molten alloy; Forming a metallic glass coating comprising; And Converting at least a portion of the metallic glass coating into a crystalline material having a nanocrystalline particle size and a second hardness of at least 9.2 GPa, Method of Forming a Cured Surface on a Substrate. The method of claim 1, wherein the substrate is a metal material. The method of claim 1, wherein the substrate is a ceramic material. 3. The method of claim 2, wherein said first hardness is at least 10.0 GPa. The method of claim 1, wherein the metallic glass coating is applied to the substrate as a plasma spray. The method of claim 1, wherein forming the metallic glass coating comprises applying an atomized powder of metallic glass material over the substrate. 3. The method of claim 2, wherein forming the metallic glass coating comprises forming a continuous accumulation of continuous layers. 3. The method of claim 2, wherein said converting step comprises heating the metal glass to at least the crystallization temperature of the metal glass. The method of claim 10, wherein the heating step comprises heating to a temperature of at least 600 ° C. and below the melting temperature of the metal glass. 3. The method of claim 2, wherein said second hardness is at least 10.0 GPa. The method of claim 1, wherein the metallic glass coating is applied to the substrate by a plasma spray system. 2. The method of claim 1, wherein forming the metallic glass coating comprises applying a spray powder of metallic glass material over the substrate.

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