US2017129016A1PendingUtilityA1

Powdered metal alloy composition for wear and temperature resistance applications and method of producing same

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Assignee: FEDERAL MOGUL CORPPriority: Apr 8, 2008Filed: Jan 13, 2017Published: May 11, 2017
Est. expiryApr 8, 2028(~1.7 yrs left)· nominal 20-yr term from priority
Inventors:Denis B. Christopherson, Jr.Leslie John FarthingTodd SchoenwetterGilles L'EsperancePhilippe Beaulieu
B22F 2009/0828C22C 38/24C22C 33/0292C22C 33/0285B22F 1/00C22C 37/06C22C 38/36B22F 2998/10C22C 38/22B22F 9/082
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Claims

Abstract

A powder metal steel alloy composition for high wear and temperature applications is made by water atomizing a molten steel alloy composition containing C in an amount of at least 3.0 wt %; at least one carbide-forming alloy element selected from the group consisting of: Cr, V, Mo or W; an O content less than about 0.5 wt %, and the balance comprising essentially Fe apart from incidental impurities. The high carbon content reduces the solubility of oxygen in the melt and thus lowers the oxygen content to a level below which would cause the carbide-forming element(s) to oxidize during water atomization. The alloy elements are thus not tied up as oxides and are available to rapidly and readily form carbides in a subsequent sintering stage. The carbon, present in excess, is also available for diffusing into one or more other admixed powders that may be added to the prealloyed powder during sintering to control microstructure and properties of the final part.

Claims

exact text as granted — not AI-modified
What is claimed is: 
     
         1 . A method of making powdered metal, comprising:
 preparing a molten steel alloy composition containing C, at least one carbide-forming alloy element selected from the group consisting of Cr, V, Mo or W, and the balance comprising essentially Fe apart from incidental impurities;   water atomizing the molten alloy to yield prealloyed powder metal particles; and   during the preparation of the molten steel alloy, controlling the amount of carbon added so that the carbon content exceeds that required to combine with the at least one carbide forming alloy element to produce carbides during a subsequent sintering stage, and thereby defining an excess carbon constituent which has the effect of decreasing the solubility of oxygen in the molten steel alloy and protecting the at least one carbide-forming alloy element from substantially oxidizing during the water atomization.   
     
     
         2 . The method of  claim 1 , wherein the carbon content is at least 3.0 wt % and having an O content less than about 0.5 wt %. 
     
     
         3 . The method of  claim 1  including selecting at least Cr as the carbide-forming alloy clement in an amount greater than 10 wt %. 
     
     
         4 . The method of  claim 3 , including selecting the Cr content to be about 13 wt %. 
     
     
         5 . The method of  claim 1  including selecting at least Mo as the carbide-forming alloy element in an amount below 5 wt %. 
     
     
         6 . The method of  claim 1  wherein the at least one carbide-forming alloy element is supersaturated in the water-atomized powder. 
     
     
         7 . The method of  claim 1 , including compacting and sintering the powder metal and causing the carbon to combine with the at least one carbide-forming alloy element to form carbides. 
     
     
         8 . The method of  claim 7 , including admixing the prealloyed powder with another powder and causing at least some of the carbon in the prealloyed powder to diffuse into the admixed powder during sintering. 
     
     
         9 . The method of  claim 1 , including mechanically grinding the prealloyed powder prior to sintering. 
     
     
         10 . The method of  claim 1 , including annealing the prealloyed powder prior to sintering, wherein at least a fraction of the at least one carbide-forming alloy clement is present in a supersaturated state. 
     
     
         11 . The method of  claim 1 , wherein the prealloyed powder is unannealed and unground before sintering. 
     
     
         12 . The method of  claim 1 , wherein Cr is at about 13 wt %, Mo is at about 1,5 and further including V at about 4 wt% and W at about 2.5 wt%. 
     
     
         13 . A method for making a sintered comprising:
 preparing a molten steel alloy composition containing C in an amount of at least 3.0 wt%; at least one carbide-forming alloy element selected from the group consisting of: Cr, V, Mo or W; an O content less than about 0.5 wt %, and the balance comprising essentially Fe apart from incidental impurities;   water atomizing the molten steel alloy to produce prealloyed powder;   compacting and sintering the prealloyed powder either alone or admixed with another powder to cause the carbon to combine with the at least one carbide-forming alloy element to produce carbides.   
     
     
         14 . The method of  claim 13 , wherein following water atomization, the at least one carbide-forming alloy element is supersaturated. 
     
     
         15 . The method of  claim 13 , wherein the prealloyed powder is admixed with another powder and during sintering, some of the carbon diffuses from the prealloyed powder into the admixed powder. 
     
     
         16 . The method of  claim 13 , wherein during sintering, the carbon in the prealloyed powder combines with the at least one carbide-forming alloy element to form carbides. 
     
     
         17 . The method of  claim 14 , wherein the sintered prealloyed particles have a volume fraction of chromium rich carbides of at least 40 vol %. 
     
     
         18 . The method of  claim 15 , wherein the sintered prealloyed particles have a volume fraction of chromium-rich carbides of about 45 vol %. 
     
     
         19 . The method of  claim 15 , wherein the sintered prealloyed particles have a volume fraction of vanadium-rich carbides of about 7 vol %. 
     
     
         20 . The method of  claim 16 , wherein the sintered prealloyed particles have a volume fraction of vanadium-rich carbides of about 7 vol %. 
     
     
         21 . The method of  claim 14 , wherein the sintered prealloyed particles have a volume fraction of carbides of at least 47 vol %. 
     
     
         22 . The method of  claim 19 , wherein the carbides have a size of about 1-2 μm. 
     
     
         23 . The method of  claim 13 , wherein Cr is present at about 13 wt %, Mo is present at about 1.5 wt %, V is present at about 4 wt % and W is present at about 2.5 wt %. 
     
     
         24 . The method of  claim 13 , wherein Cr is present above 10 wt % and Mo is present below 5 wt%. 
     
     
         25 . The method of  claim 13 , wherein the sintered prealloyed powder has a microhardness of 1000-1200 Hv 50 . 26, A sintered powder metal composition, comprising:
 at least a fraction of prealloyed water-atomized steel powder containing C in an amount of at least 3.0 wt %; Cr in an amount of about 13 wt %; Mo in an amount of about 1.5 wt %; V in an amount of about 4 wt %; W in an amount of about 2.5 wt %; an O content of less than about 0.5 wt %, and the balance comprising essentially Fe apart from incidental impurities.   
     
     
         27 . The composition of claim  26 , wherein the prealloyed water-atomized steel powder contains C in an amount of about 3.8 wt %. 
     
     
         28 . The composition of  claim 27  including chromium-rich carbides in an amount of about 40-45 vol. %. 
     
     
         29 . The composition of  claim 28  including vanadium rich carbides in an amount of about 7 vol. %.

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