Encapsulated Wear Particles

Abstract

Incorporating hard particles in a matrix forming the surface of a member can significantly increase wear resistance. Practical use of diamond in industrial applications is limited as the carbon structure breaks down to graphite in air at temperatures over 700° C. When exposed to molten iron the diamond surface can also chemically react and dissolve into the iron. Metal compounds that coat the diamond can provide one or more protective layers that limit contact of the diamond surface with elements that will degrade its structure. Coating can also provide a wettable surface for the molten matrix during processing to improve retention of the particle in the matrix.

1 . A wear particle for inclusion in a ferrous matrix comprising:
 a diamond particle;   an inner layer on the surface of the diamond; and   an outer layer to bind with the ferrous matrix.   
     
     
         2 . The wear particle of  claim 1  where the inner layer and the outer layer each comprise a metal compound. 
     
     
         3 . The wear particle of  claim 1  where the inner layer is a metal carbide. 
     
     
         4 . The wear particle of  claim 1  where the outer layer is a metal nitride. 
     
     
         5 . The wear particle of  claim 1  where the composition of the outer layer promotes wetting of the wear particle by the molten matrix. 
     
     
         6 . The wear particle of  claim 1  further including a third layer between the inner and outer layer. 
     
     
         7 . The wear particle of any of  claim 1  where the outer layer is a sub-stoichiometric nitride to promote wetting. 
     
     
         8 . The wear particle of any of  claim 1  where each layer comprises a metal compound that includes one or more of silicon, tungsten, titanium, nickel, boron, niobium, tantalum, zirconium, hafnium, molybdenum and aluminum. 
     
     
         9 . The wear particle of  claim 1  where the inner layer is a metal compound and the outer layer is a metal compound incorporating a different metal than the inner layer. 
     
     
         10 . A cast wear member incorporating diamond particles, the diamond particles including:
 a primary layer on the surface of the diamond; and   a tertiary layer to bind with the metal of the cast wear member.   
     
     
         11 . The cast wear member of  claim 10  where the wear member is a ferrous material. 
     
     
         12 . The cast wear member of  claim 10  where the primary layer is a carbide. 
     
     
         13 . The cast wear member of  claim 10  where the tertiary layer is a nitride. 
     
     
         14 . The cast wear member of  claim 10  where the tertiary layer promotes wetting of the wear particle by the wear member molten matrix. 
     
     
         15 . The cast wear member of  claim 10  where the tertiary layer is a sub-stoichiometric nitride to promote wetting. 
     
     
         16 . The cast wear member of  claim 10  where each layer comprises a metal compound that includes one or more of silicon, tungsten, titanium, nickel, boron, niobium, tantalum, zirconium, hafnium, molybdenum and aluminum. 
     
     
         17 . The cast wear member of  claim 10  where the member has a working portion and a mounting portion and diamond is preferentially distributed in the working portion. 
     
     
         18 . The cast wear member of  claim 17  where the mounting portion is substantially free of diamond. 
     
     
         19 . A method of incorporating diamond during casting of a wear member comprising:
 depositing a protective coating on the surface of the diamond;   depositing a coating on the protective coating.   
     
     
         20 . The method of incorporating diamond of  claim 19  where depositing a coating includes chemical vapor deposition. 
     
     
         21 . The method of incorporating diamond of  claim 19  where depositing a coating includes physical vapor deposition. 
     
     
         22 . The method of incorporating diamond of  claim 19  where the coatings comprise a metal compound that includes one or more of silicon, tungsten, titanium, nickel, boron, niobium, tantalum, zirconium, hafnium, molybdenum and aluminum. 
     
     
         23 . The method of incorporating diamond of  claim 19  where the protective coating is a metal carbide. 
     
     
         24 . The method of incorporating diamond of  claim 19  where the protective coating resists degradation of the diamond by contact with a ferrous matrix. 
     
     
         25 . The method of incorporating diamond of  claim 19  where the coating on the protective coating is a metal nitride. 
     
     
         26 . The method of incorporating diamond of  claim 19  where the coating on the protective coating is a metal carbonitride. 
     
     
         27 . The method of incorporating diamond of  claim 19  further including depositing a third coating that is a sub stoichiometric metal nitride to promote wetting of the coated diamond by the molten metal. 
     
     
         28 . The method of incorporating diamond of  claim 19  further including depositing a third coating that is a sub stoichiometric metal carbonitride to promote wetting of the coated diamond by the molten metal. 
     
     
         29 . The method of incorporating diamond of  claim 19  where the metal of the protective coating and the metal of the coating on the protective coating are different metals. 
     
     
         30 . The method of incorporating diamond of  claim 19  where incorporating the diamond in the cast metal includes suspending coated diamond particles in a mold prior to pouring molten metal for the wear member. 
     
     
         31 . The method of incorporating diamond of  claim 19  where coated diamond particles are introduced into a mold simultaneous to the molten metal for the wear member. 
     
     
         32 . The method of incorporating diamond of  claim 19  further including doping the diamond with one or more elements to alter the electrical conductivity of the diamond. 
     
     
         33 . An article for abrasive environments comprising a metallic body and hard particles within the metallic body, the hard particles each including a superabrasive core, a first metal carbide layer at least partially coating the superabrasive core, and a second metal nitride layer at least partially coating the first metal carbide layer. 
     
     
         34 . The article of  claim 33  where the metallic body is ferrous. 
     
     
         35 . The article of  claim 33  including an outer layer on the second layer where the composition of the outer layer is a sub-stoichiometric nitride. 
     
     
         36 . The article of  claim 33  where each layer comprises a metal compound that includes one or more of silicon, tungsten, titanium, nickel, boron, niobium, tantalum, zirconium, hafnium, molybdenum and aluminum. 
     
     
         37 . An article for abrasive environments comprising a metallic body and hard particles within the metallic body, the hard particles each including a superabrasive core at least partially coated by a metal nitride layer. 
     
     
         38 . An article for abrasive environments comprising a metallic body composed of a ferrous-based alloy and diamond particles contained within the metallic body, wherein the diamond particles are coated by an inner metal carbide layer and an outer metal nitride layer. 
     
     
         39 . The article of  claim 38  where the inner metal layer completely covers the diamond particle. 
     
     
         40 . The article of  claim 38  where the outer metal layer completely covers the inner metal layer. 
     
     
         41 . The article of  claim 38  where each layer comprises a metal compound that includes one or more of silicon, tungsten, titanium, nickel, boron, niobium, tantalum, zirconium, hafnium, molybdenum and aluminum. 
     
     
         42 . An article for abrasive environments comprising a metallic body composed of a ferrous-based alloy and diamond particles contained within the metallic body, wherein the diamond particles are coated by a metal nitride layer. 
     
     
         43 . The article of  claim 42  where the metal nitride layer completely covers the diamond particle. 
     
     
         44 . The article of  claim 42  where an outer substoichiometric metal compound layer coats the metal nitride layer. 
     
     
         45 . The article of  claim 44  where each layer comprises a metal compound that includes one or more of silicon, tungsten, titanium, nickel, boron, niobium, tantalum, zirconium, hafnium, molybdenum and aluminum. 
     
     
         46 . A wear part for earthworking equipment comprising a wearable body having a base to mount to the earthworking equipment and a wear surface to contact earthen material, wherein at least a portion of the wear surface includes a coated diamond grit. 
     
     
         47 . The wear part for earthworking equipment of  claim 46  where the wearable body is a tooth or a shroud for a bucket. 
     
     
         48 . The wear part for earthworking equipment of  claim 46  where the wearable body is a tooth for a dredge. 
     
     
         49 . The wear part for earthworking equipment of  claim 46  where the wearable body is installed in a crusher. 
     
     
         50 . A process for manufacturing an article for an abrasive environment comprising securing coated diamond grit to a casting surface within a mold, feeding a melted ferrous-based alloy into the mold such that the melted ferrous-based alloy receives the coated diamond grit to form the article, and removing the mold from the article. 
     
     
         51 . The process for manufacturing of  claim 50  where the diamond grit is secured to the casting surface using a sacrificial medium such as a mesh or cloth, a metal ribbon, metal foam or ceramic foam. 
     
     
         52 . The process for manufacturing of  claim 50  where the diamond grit is secured to the casting surface with a precursor matrix material. 
     
     
         53 . A process for manufacturing an article for an abrasive environment comprising securing hard particles including superabrasive cores coated with a first metal carbide layer and a second metal nitride layer to a casting surface within a mold, feeding a ferrous molten metal into the mold where the molten metal receives the hard particles, and removing the mold from the article. 
     
     
         54 . The process for manufacturing of  claim 53  where the super abrasive cores are painted on the casting surface. 
     
     
         55 . A process for manufacturing an article for an abrasive environment comprising securing hard particles coated by an inner metal carbide layer and an outer metal nitride layer to an inner surface of a mold, feeding a metallic-based powder into the mold, heating the mold to sinter the powder into a solid body containing the hard particles, and removing the mold.