Methods for preparing metallurgical powder compositions and compacted articles made from the same

Abstract

Provided are methods of preparing high density compacted components that increase that lubricity of metallurgical powder compositions while reducing the overall organic content of the compacted component. Method of preparing high density compacted components having a high density include the steps of providing a metallurgical powder composition having particles at least partially coated with a metal phosphate layer, and compacting the metallurgical powder composition in the die at a pressure of at least about 5 tsi. The metallurgical powder composition comprises a base-metal powder, optional alloying powders, and a particulate internal lubricant. The metal phosphate at least partially coats the base-metal powder, the optional alloying powder, or both. The metal phosphate coating increases the lubricity of metallurgical powders without the need for large quantities of organic material, e.g., lubricants and binders.

What is claimed: 
     
         1 . A method of preparing a metallurgical powder composition comprising:
 (a) providing an iron-based metal powder,   (b) providing a coating solution comprising a metal phosphate and a protonic acid, and   (c) contacting the particles of the iron-based powder with the coating solution so as to at least partially coat the particles with the metal phosphate.   
     
     
         2 . The method of preparing a metallurgical powder composition of  claim 1 , further comprising a step of providing a particulate internal lubricant. 
     
     
         3 . The method of preparing a metallurgical powder composition of  claim 2 , wherein the metallurgical powder composition comprises from about 0.01 to about 2.0 weight percent by weight of a particulate internal lubricant. 
     
     
         4 . The method of preparing a metallurgical powder composition of  claim 1  further comprising the step of admixing a particulate internal lubricant with the iron-based metal powder prior to being coated with the metal phosphate, the particulate internal lubricant thereby also being contacted with the coating solution. 
     
     
         5 . The method of preparing a metallurgical powder composition of  claim 1  further comprising the step of admixing a particulate internal lubricant with the iron-based metal powder after the iron-based metal powder is coated with the metal phosphate. 
     
     
         6 . The method of preparing a metallurgical powder composition of  claim 2  wherein the iron-based metal powder is bonded with about 0.10 weight percent binding agent, and the particulate internal lubricant comprises:
 about 0.15 weight percent of a polyamide lubricant composed of ethylene bis-stearamide having an initial melting point between about 200° C. and 300° C., and 
 about 0.15 weight percent of Kenolube™. 
 
     
     
         7 . The method of preparing a metallurgical powder composition of  claim 2 , wherein the particulate internal lubricant comprises:
 about 0.2 weight percent of a polyamide lubricant composed of ethylene bis-stearamide having an initial melting point between about 200° C. and 300° C., and   about 0.2 weight percent of Kenolube™.   
     
     
         8 . The method of preparing a metallurgical powder composition of  claim 1 , further comprising a step of admixing an alloying powder with the iron-based metal powder after the base metal powder is coated with the metal phosphate. 
     
     
         9 . The method of preparing a metallurgical powder composition of  claim 8 , wherein the alloying powder comprises graphite, Ni, Cu, FeP, ferroalloy, or a combination thereof. 
     
     
         10 . The method of preparing a metallurgical powder composition of  claim 1 , wherein the metallurgical powder composition comprises from about 0.05 to about 1.0 weight percent of the metal phosphate. 
     
     
         11 . The method of preparing a metallurgical powder composition of  claim 1 , wherein the iron based metal powder comprises an alloying powder. 
     
     
         12 . The method of preparing a metallurgical powder composition of  claim 1 , wherein the iron based metal powder is a prealloyed iron base metal powder. 
     
     
         13 . The method of preparing a metallurgical powder composition of  claim 1 , wherein the iron based metal powder is a diffusion bonded iron based metal powder. 
     
     
         14 . The method of preparing a metallurgical powder composition of  claim 1 , wherein the iron based metal powder is a ferromagnetic powder. 
     
     
         15 . A method of preparing a compacted article comprising the steps of:
 (a) providing a metallurgical powder composition comprising:
 (i) at least 85 weight percent of an iron-based metal powder; and 
 (ii) from about 0.01 to about 1.0 weight percent, based on the weight of the iron-based metal powder, of metal phosphate that at least partially coats the iron-based metal powder; 
   (b) compacting the metallurgical powder composition in a die at a pressure of at least about 5 tsi.   
     
     
         16 . The method of  claim 15 , further comprising the step of sintering the compact part. 
     
     
         17 . The method of  claim 15 , wherein said metal phosphate is manganese zinc phosphate, nickel phosphate, zinc phosphate, copper phosphate, or combinations thereof. 
     
     
         18 . The method  claim 15 , wherein the metal phosphate is present in an amount from about 0.05 to about 0.40 weight percent by weight of base-metal powder. 
     
     
         19 . The method of  claim 15 , wherein the metallurgical powder composition further comprises a particulate internal lubricant. 
     
     
         20 . The method of  claim 19 , wherein the particulate internal lubricant is present in an amount from about 0.01 to about 2.0 weight percent by weight of base-metal powder. 
     
     
         21 . The method of  claim 19 , wherein the particulate internal lubricant is a polyamide, a C 5  to C 30  fatty acid, a metal salt of a polyamide, a metal salt of a C 5  to C 30  fatty acid, an ammonium salt of a C 5  to C 30  fatty acid, lithium stearate, zinc stearate, manganese stearate, calcium stearate, ethylene bis-stearamide, polyethylene wax, polyolefin, or a combination thereof. 
     
     
         22 . The method of  claim 15 , wherein the iron based metal powder comprises an alloying powder. 
     
     
         23 . The method of  claim 22 , wherein the iron based metal powder is a prealloyed iron base powder. 
     
     
         24 . The method of  claim 15 , wherein the iron based metal powder is a diffusion bonded iron based powder. 
     
     
         25 . The method of  claim 15 , wherein the iron based metal powder is a ferromagnetic powder. 
     
     
         26 . The method of  claim 15 , wherein the iron-based metal powder is coated by the steps comprising:
 (a) providing an iron-based metal powder,   (b) providing a coating solution of metal phosphate and protonic acid,   (c) contacting the iron based particles with the coating solution to at least partially coat said iron particles with the metal phosphate.   
     
     
         27 . The method of  claim 26 , wherein the protonic acid is diluted in acetone. 
     
     
         28 . The method of  claim 26 , wherein the protonic acid is sulphuric acid, nitric acid, hydrochloric acid, phosphoric acid, or combinations thereof. 
     
     
         29 . The method of  claim 26 , further comprising the step of sintering the compacted metallurgical powder composition.