FIELD OF THE INVENTION
The present invention is directed to treated grinding articles and methods for forming treated grinding articles. More particularly, the present invention is directed to mineral grinding articles having a plurality of particles dispersed in a material having reduced hardness compared to the plurality of particles.
BACKGROUND OF THE INVENTION
Coal crusher rolls are used to crush coal which is fed to a boiler for producing steam, reducing the size of the coal units from about 20 mm to about 200 mesh size. During the crushing process, the grinding surfaces of the coal crusher rolls become worn due to the inherent abrasive nature of the coal which is being crushed. Coals which have elevated ash content are typically more abrasive than coals with lower ash content, and may cause faster erosion of the grinding surfaces of the coal crusher roles, both by attrition and wear from the crushing loads applied on the coal crusher rolls. Further degradation of the coal crusher rolls may be caused by contaminants in the coal supply such as iron and stone, which may cause sudden impacts when introduced into the coal crusher.
During production or operation of coal crusher rolls, cracks may form, either in coatings applied to a substrate of the coal crusher rolls or in the substrates of the coal crusher rolls. The presence of such cracks, either in the substrates or in the coatings applied to the substrates, may increase the rates of attrition and wear during coal crushing operations.
Coal crusher rolls may be encased in sinter-cast materials to extend the useful life, but such solutions are expensive and are limited in the increase in useful life they provide.
BRIEF DESCRIPTION OF THE INVENTION
In an exemplary embodiment, a method for forming a treated grinding article includes applying a slurry coating material to a grinding article. The grinding

article includes a substrate having a metal alloy composition and at least one crack penetrating from a surface of the grinding article into the grinding article. The slurry coating material includes a matrix material, a braze material, and a plurality of particles. The plurality of particles include a higher hardness than the substrate. The slurry coating material is infused into the at least one crack. The grinding article and the slurry coating material are heat treated, and the at least one crack is sealed. A treatment is formed from the coating slurry material, and a grinding surface is formed. The treatment includes a higher wear-resistance than the substrate.
In another exemplary embodiment, a treated grinding article includes a substrate having a metal alloy composition, at least one crack, a treatment disposed in and sealing the at least one crack, and a grinding surface. The treatment includes a matrix material, a braze material, a plurality of particles, and a higher wear-resistance than the substrate. The plurality of particles includes an elevated hardness relative to the substrate.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an assembly, according to an embodiment of the present disclosure.
FIG. 2 is a sectional view of a grinding article, according to an embodiment of the present disclosure.
FIG. 3 is a sectional view of the article of FIG. 2 following application of the slurry coating material, according to an embodiment of the present disclosure.
FIG. 4 is a sectional view of the article of FIG. 3 following heat treatment of the

article, corresponding to the treated article of FIG. 1 taken along lines 4–4, according to an embodiment of the present disclosure.
FIG. 5 is a sectional view of the article of FIG. 4 following application of a grinding coating, according to an embodiment of the present disclosure.
FIG. 6 is a sectional view of a grinding article having a coating, according to an embodiment of the present disclosure.
FIG. 7 is a sectional view of the article having a coating of FIG. 6 following application of the slurry coating material, according to an embodiment of the present disclosure.
FIG. 8 is a sectional view of the article having a coating of FIG. 7 following heat treatment of the article, corresponding to the treated article of FIG. 1 taken along lines 8–8, according to an embodiment of the present disclosure.
FIG. 9 is a sectional view of the article having a coating of FIG. 8 following application of a grinding coating, according to an embodiment of the present disclosure.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
DETAILED DESCRIPTION OF THE INVENTION
Provided are exemplary treated grinding articles, and methods for forming the treated grinding articles. Embodiments of the present disclosure, in comparison to articles and methods not utilizing one or more features disclosed herein, decrease costs, increase process efficiency, increase durability, increase reliability, increase service lifetime, decrease erosion, decrease wear, or a combination thereof.
Referring to FIGS. 2 and 6, in one embodiment, a grinding article 200 includes a substrate 202 having a metal alloy composition 204, and at least one crack 206 penetrating from a surface of the grinding article 208 into the grinding article 200.

Referring to FIGS. 1, 3, and 7, a method for forming a treated grinding article 100 includes applying a slurry coating material 300 to the grinding article 200. The slurry coating material 300 includes a matrix material 302, a braze material 304, and a plurality of particles 306. The plurality of particles 306 includes a higher hardness than the substrate 202. The slurry coating material 300 is infused into the at least one crack 206. Referring to FIGS. 3 and 7, and 4 and 8, the grinding article 200 and the slurry coating material 300 are heat treated, and the at least one crack 206 is sealed. A treatment 400 is formed from the slurry coating material 300, and a grinding surface 402 is formed. The treatment 400 includes a higher wear-resistance than the substrate 202.
Referring to FIG. 1, the treated grinding article 100 may be any suitable article. In one embodiment, the treated grinding article 100 is a grinding roll 102 such as, but not limited to, a coal grinding roll. The grinding roll 102 may be an independent component or the grinding roll 102 may be a component of a grinding apparatus 104, such as, but not limited to, a bowl mill, a ball and race mill, a drum and ball mill, a coal crusher, or combinations thereof.
Referring to FIG. 2, in one embodiment, the surface of the grinding article 208 is a substrate surface 210, and the at least one crack 206 penetrates from the substrate surface 210 into the substrate 202. The substrate 202 may include any suitable material, including, but not limited to a chrome-iron alloy including, by weight, at least about 30% chrome, cast iron, spheroidal graphite iron, tempered ductile iron, 4140 steel alloys, 4340 steel alloys, white cast iron, cast iron including niobium, cast iron including chromium, cast iron including titanium, Hadfield steel (MANGALLOY®), cast steel, locomotive wheel steel (class A or equivalent grade), rail steel, or combinations thereof.
Referring to FIG. 6, in another embodiment, the surface of the grinding article 208 is a coating surface 602 of a coating 600 disposed on a substrate 202 of the grinding article 200, and the at least one crack 206 penetrates from the coating surface 602 into the coating 600. In a further embodiment (not shown), the at least

one crack 206 penetrates from the coating surface 602 into the coating 600 and continues into the substrate 202. The coating 600 may include any suitable coating-type, including, but not limited to, a bond coat, an abrasive coating, a grinding coating 500, a thermal barrier coating, an environmental barrier coating, a diffusion aluminide coating, or combinations thereof. Suitable bond coats include, but are not limited to, molybdenum, Ni-5Al, Ni-20Al, Ni-20Cr, MCrAlY (where M is nickel, cobalt, or iron), or combinations thereof.
Referring to FIGS. 3 and 7, the matrix material 302 may include any suitable composition, including, but not limited to, cobalt-chromium alloys, nickel-chromium alloys, white cast iron alloys having chromium content of at least about 15 wt% as well as up to about 10 wt% of a least one of titanium, vanadium, molybdenum, and niobium, Hadfield steel alloys, high chromium steel alloys, steel alloys including at least one of molybdenum carbide and tungsten carbide, or combinations thereof.
The braze material 304 may include any suitable composition, including, but not limited to, NiCrBSi alloys, CoCrBSi alloys, or combinations thereof.
The plurality of particles 306 dispersed in the slurry coating material 300 may include any suitable composition, including, but not limited to, a plurality of ceramic particles. Suitable ceramic particles may include, but are not limited to, metal carbides, metal borides, metal oxides, boron nitrides, boron carbides, boron carbon nitrides, zirconia toughened aluminas, silicon carbides, silicon nitrides, silicon oxy-nitrides, silicon aluminum oxy-nitrides, or combinations thereof. The plurality of particles 306 may include any suitable particle size distribution, including, but not limited to, a particle size distribution of up to about 10 nm, alternatively up to about 20 nm, alternatively up to about 25 nm, alternatively up to about 10 mm, alternatively up to about 20 mm, alternatively up to about 25 mm, alternatively from about 1 nm to about 25 mm, alternatively from about 1 nm to about 25 nm, alternatively from about 1 mm to about 25 mm. In one embodiment, the plurality of particles 306 includes a plurality of fine particles

having a fine particle size distribution up to about 25 nm, and a plurality of coarse particles having a coarse particle size distribution from about 1 mm to about 25 mm, the plurality of fine particles and the plurality of coarse particles being intermixed. The intermixed plurality of fine particles and plurality of coarse particles may be distributed to optimize protection against erodent abrasive particles having different sizes. The plurality of fine particles in the plurality of particles 306 may also fill in gaps which may be present between the plurality of coarse particles in the plurality of particles 306, thereby enhancing the resistance of the plurality of particles 306 to erosion and abrasion.
Applying the slurry coating material 300 may include any suitable technique, including, but not limited to, spraying, dipping, painting, brushing, or combinations thereof. The slurry coating material 300 may be applied over the entire surface of the grinding article 208 or over a portion of the surface of the grinding article 208 being less than the entirety of the surface of the grinding article 208. In one embodiment, the portion of the surface of the grinding article 208 is adjacent to the at least one crack 206.
In one embodiment, the slurry coating material 300 includes, by weight, between about 1% to about 25% of the braze material 304, alternatively between about 5% to about 15% of the braze material 304, alternatively between about 7% and about 12% of the braze material 304, alternatively about 10% of the braze material 304, between about 1% to about 50% of the matrix material 302, alternatively between about 2% to about 40% of the matrix material 302, alternatively between about 5% to about 35% of the matrix material 302, alternatively between about 10% to about 30% of the matrix material 302, alternatively between about 15% to about 25% of the matrix material 302, alternatively about 20% of the matrix material 302, and a balance of the plurality of particles 306.
Referring to FIGS. 3 and 7 and 4 and 8, heat treating the grinding article 200 and the slurry coating material 300 may include any suitable temperature and duration. Suitable temperatures may include, but are not limited to, temperatures between

about 500 °C to about 1,500 °C, alternatively between about 550 °C to about 1,400 °C, alternatively between about 600 °C to about 1,300 °C, alternatively between about 650 °C to about 1,200 °C, alternatively between about 700 °C to about 1,100 °C, alternatively between about 700 °C to about 900 °C, alternatively between about 800 °C to about 1,000 °C, alternatively between about 900 °C to about 1,100 °C, alternatively at least about 600 °C, alternatively at least about 700 °C, alternatively at least about 800 °C, alternatively at least about 900 °C, alternatively at least about 1,000 °C, alternatively at least about 1,100 °C. Suitable durations may include, but are not limited to, durations between 0.5 hours to about 6 hours, alternatively between about 1 hour and about 4 hours, alternatively between about 1 hour and about 2 hours, alternatively between about 2 hours and about 3 hours, alternatively between about 3 hours and about 4 hours, alternatively at least about 1 hour, alternatively at least about 2 hours, alternatively at least about 3 hours, alternatively at least about 4 hours.
In one embodiment, heat treating the grinding article 200 and the slurry coating material 300 metallurgically bonds the treatment 400 to the grinding article 200. In another embodiment, heat treating the grinding article 200 and the slurry coating material 300 mechanically bonds the treatment 400 to the grinding article 200.
Forming the treatment 400 may include any suitable finishing technique, including, but not limited to, machining, buffing, grinding, polishing, belting, or combinations thereof.
The plurality of particles 306 may be randomly dispersed in the treatment 400, multi-modally dispersed in the treatment 400, essentially uniformly dispersed in the treatment 400, uniformly dispersed in the treatment 400, dispersed in the treatment 400 per a predetermined pattern, or combinations thereof. As used herein, “multi-modally dispersed” indicates a region having a greater concentration and a region having a lesser concentration, and “essentially uniformly dispersed” indicates a variance in concentration of less than about 20%,

alternatively, less than about 15%, alternatively less than about 10%, alternatively less than about 5%, alternatively less than about 1%. “Multi-modally dispersed” further may refer to the distribution of different sizes within the plurality of particles 306.
In one embodiment, the plurality of particles 306 is dispersed in the treatment 400 at a density (average, by weight) of at least about 50%, alternatively at least about 55%, alternatively at least about 60%, alternatively at least about 65%, alternatively at least about 75%, alternatively at least about 80%, alternatively at least about 85%, alternatively at least about 90%, alternatively between about 50% to about 99%, alternatively between about 60% to about 95%, alternatively between about 75% to about 94%, alternatively between about 85% to about 93%, alternatively between about 90% to about 95%, alternatively about 93%.
Referring to FIG. 4, in one embodiment, forming the treatment 400 includes forming a treatment surface 404 substantially flush with the surface of the grinding article 208 (whether of the substrate 202 (shown) or the coating 600 (not shown)). As used herein, “substantially flush” indicates that the treatment surface 404 is neither elevated nor depressed relative to the surface of the grinding article 208 where the treatment surface 404 and the surface of the grinding article 208 meet by more than about 1 mm. The treatment surface 404 may be essentially crack-free, alternatively crack-free.
The treatment 400 may include any suitable hardness, including, but not limited to a hardness of at least about 900 VPN, alternatively at least about 950 VPN, alternatively at least about 1,000 VPN, alternatively at least about 1,050 VPN, alternatively at least about 1,100 VPN, alternatively at least about 1,150 VPN, alternatively between about at least about 800 VPN and about 1,500 VPN, alternatively between about at least about 900 VPN and about 1,400 VPN, alternatively between about at least about 950 VPN and about 1,300 VPN, alternatively between about at least about 1,000 VPN and about 1,200 VPN.
Referring to FIG. 8, in another embodiment, forming the treatment 400 includes

forming a treatment coating 800 disposed on the grinding article 200 (whether the grinding article includes the coating 600 (shown) or not). The treatment coating 800 includes a treatment surface 802 disposed above the surface of the grinding article 208. The treatment coating 800 may include any suitable thickness, including, but not limited to, a treatment coating thickness 804 of between about 0.1 mm and about 10 mm, alternatively between about 0.25 mm and about 5 mm, alternatively between about 0.5 mm and about 3 mm.
Referring to FIGS. 4 and 8, in one embodiment, a treated grinding article 100 includes the substrate 202 having the metal alloy composition 204, the at least one crack 206, the treatment 400 disposed in and sealing the at least one crack 206, and the grinding surface 402. The treatment 400 includes the matrix material 302, the braze material 304, and the plurality of particles 306. The plurality of particles 306 includes a higher hardness than the substrate 202, and the treatment 400 includes elevated wear-resistance relative to the substrate 202.
Referring to FIGS. 5 and 9, in one embodiment, a grinding coating 500 may be deposited on the treatment 400, forming the grinding surface 402. Applying the grinding coating 500 may include any suitable technique selected, including, but not limited to, thermal spraying, cored wire arc spraying, wire arc spraying, high velocity air fuel spraying, cold spraying, welding, cladding, composite coating by plating, composite coating by electro-less plating, or combinations thereof.
The grinding coating 500 may be disposed directly on the treatment 400 or may be disposed on an intermediate layer (not shown) such as a bond coat. The grinding coating 500 may include any suitable thickness, including, but not limited to, a grinding coating thickness 502 of between about 0.1 mm and about 10 mm, alternatively between about 0.25 mm and about 5 mm, alternatively between about 0.5 mm and about 3 mm.
In one embodiment, applying the grinding coating 500 includes forming a grinding coating matrix 504 on the treatment 400, and dispersing the plurality of particles 306 in the grinding coating matrix 504. The grinding coating matrix 504

may include any suitable material, including, but not limited to, cobalt-chromium alloys, nickel-chromium alloys, nickel aluminum alloys, iron-chromium alloys, iron-chromium-aluminum alloys, nickel-aluminum-chromium alloys, or combinations thereof. The plurality of particles 306 disposed in the grinding coating matrix 504 may include the same composition as the plurality of particles 306 disposed in the slurry coating material 300, or may include a distinct composition from the plurality of particles 306 disposed in the slurry coating material 300.
In one embodiment, the plurality of particles 306 in at least one of the treatment 400 the grinding coating 500 is essentially free of oxidation and decarburization chemical structure modifications. As used in this context, “essentially free” indicates that less than about 20%, by weight, of the plurality of particles 306 are oxidized or decarburized, alternatively less than about 15%, by weight, alternatively less than about 10%, by weight, alternatively less than about 5%, by weight, alternatively less than about 1%, by weight, alternatively less than about 0.5%, by weight.
The plurality of particles 306 may be randomly dispersed in the grinding coating matrix 504, multi-modally dispersed in the grinding coating matrix 504, essentially uniformly dispersed in the grinding coating matrix 504, uniformly dispersed in the grinding coating matrix 504, dispersed in the grinding coating matrix 504 per a predetermined pattern, or combinations thereof. In one embodiment, the plurality of particles 306 is dispersed in the grinding coating matrix 504 at a density (average, by weight) of at least about 50%, alternatively at least about 55%, alternatively at least about 60%, alternatively at least about 65%, alternatively at least about 75%, alternatively at least about 80%, alternatively at least about 85%, alternatively at least about 90%, alternatively between about 50% to about 99%, alternatively between about 60% to about 95%, alternatively between about 75% to about 94%, alternatively between about 85% to about 93%, alternatively between about 90% to about 95%, alternatively about 93%.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

WE CLAIM:
1. A method for forming a treated grinding article, comprising:
applying a slurry coating material to a grinding article, the grinding article including a substrate having a metal alloy composition and at least one crack penetrating from a surface of the grinding article into the grinding article, the slurry coating material including: a matrix material; a braze material; and
a plurality of particles, the plurality of particles including a higher hardness than the substrate; infusing the slurry coating material into the at least one crack; heat treating the grinding article and the slurry coating material; sealing the at least one crack;
forming a treatment from the coating slurry material, the treatment including a higher wear-resistance than the substrate; and forming a grinding surface.
2. The method as claimed in claim 1, wherein the surface of the grinding article is a substrate surface, and the at least one crack penetrates into the substrate.
3. The method as claimed in claim 1, wherein the surface of the grinding article is a coating surface of a coating disposed on a substrate of the grinding article, and the at least one crack penetrates into the coating.
4. The method as claimed in claim 1, further including forming a grinding coating on the treatment.
5. The method as claimed in claim 1, wherein the slurry coating material includes, by weight:
between about 5% to about 15% of the braze material; between about 15% to about 25% of the matrix material; and a balance of the plurality of particles.

6. The method as claimed in claim 1, wherein applying the slurry coating material includes applying the matrix material selected from the group consisting of cobalt-chromium alloys, nickel-chromium alloys, white cast iron alloys having chromium content of at least about 15 wt% as well as up to about 10 wt% of a least one of titanium, vanadium, molybdenum, and niobium, Hadfield steel alloys, high chromium steel alloys, steel alloys including at least one of molybdenum carbide and tungsten carbide, and combinations thereof.
7. The method as claimed in claim 1, wherein applying the slurry coating material includes applying the braze material selected from the group consisting of NiCrBSi alloys, CoCrBSi alloys, and combinations thereof.
8. The method as claimed in claim 1, wherein applying the slurry coating material includes applying the plurality of particles dispersed in the slurry coating material including a plurality of ceramic particles, the plurality of ceramic particles being selected from the group consisting of metal carbides, metal borides, metal oxides, boron nitrides, boron carbides, boron carbon nitrides, zirconia toughened aluminas, silicon carbides, silicon nitrides, silicon oxy-nitrides, silicon aluminum oxy-nitrides, and combinations thereof.
9. The method as claimed in claim 1, wherein applying the slurry coating material includes a technique selected from the group consisting of spraying, dipping, painting, brushing, and combinations thereof.
10. The method as claimed in claim 1, wherein heat treating the grinding article and the slurry coating material includes heating the grinding article and the slurry coating material to a temperature of about 700 °C to about 1,100 °C for a duration of about 1 hour to about 4 hours.
11. The method as claimed in claim 1, wherein heat treating the grinding article and the slurry coating material metallurgically bonds the treatment to the grinding article.

12. The method as claimed in claim 1, wherein forming the treatment includes forming a treatment surface substantially flush with the surface of the grinding article.
13. The method as claimed in claim 1, wherein forming the treatment includes forming a treatment coating disposed on the grinding article, the treatment coating including a treatment surface disposed above the surface of the grinding article.
14. The method as claimed in claim 1, further including a finishing technique selected from the group consisting of machining, buffing, grinding, polishing, belting, and combinations thereof.
15. The method as claimed in claim 1, wherein the treated grinding article is a grinding roll.
16. The method as claimed in claim 15, wherein the grinding roll is a coal grinding roll.
17. A treated grinding article, comprising:
a substrate having a metal alloy composition; at least one crack;
a treatment disposed in and sealing the at least one crack, the treatment including:
a matrix material; a braze material;
a plurality of particles, the plurality of particles including a higher hardness than the substrate; and
an elevated wear-resistance relative to the substrate; and a grinding surface.
18. The treated grinding article as claimed in claim 17, further including a
grinding coating disposed on the treatment.

19. The treated grinding article as claimed in claim 17, further including a coating disposed on the substrate, the crack and treatment being disposed in the coating.
20. The treated grinding article as claimed in claim 17, wherein the treated grinding article is a grinding roll.