Hard particles for blending in sintered alloy, wear-resistant iron-based sintered alloy containing hard particles, valve seat formed of sintered alloy, and process for manufacturing hard particles

Abstract

Hard particles for blending as a starting material in a sintered alloy contain 20 to 40 mass % of molybdenum, 0.5 to 1.0 mass % of carbon, 5 to 30 mass % of nickel, 1 to 10 mass % of manganese, 1 to 10 mass % of chromium, 5 to 30 mass % of cobalt, 0.05 to 2 mass % of yttrium, and the balance being inadvertent impurities and iron.

1 . Hard particles for blending as a starting material in a sintered alloy, the hard particles consist of:
 20 to 40 mass % of molybdenum;   0.5 to 1.0 mass % of carbon,   5 to 30 mass % of nickel,   1 to 10 mass % of manganese,   1 to 10 mass % of chromium,   5 to 30 mass % of cobalt,   0.05 to 2 mass % of yttrium, and   the balance being inadvertent impurities and iron.   
     
     
         2 . The hard particles according to  claim 1 , wherein the hard particles contain from 21 to 39 mass % of molybdenum. 
     
     
         3 . The hard particles according to  claim 1 , wherein the hard particles contain from 0.7 to 0.9 mass % of carbon. 
     
     
         4 . The hard particles according to  claim 1 , wherein the hard particles contain from 6 to 28 mass % of nickel. 
     
     
         5 . The hard particles according to  claim 1 , wherein the hard particles contain from 1 to 9 mass % of manganese. 
     
     
         6 . The hard particles according to  claim 1 , wherein the hard particles contain from 2 to 9 mass % of chromium. 
     
     
         7 . The hard particles according to  claim 1 , wherein the hard particles contain from 7 to 29 mass % of cobalt. 
     
     
         8 . A wear-resistant iron-based sintered alloy, obtained by mixing a powder composed of the hard particles according to  claim 1  with a ferrous powder so as to disperse the hard particles, then sintering the mixed powders, wherein
 the hard particles account for 10 to 60 mass % of the wear-resistant iron-based sintered alloy. 
 
     
     
         9 . The wear-resistant iron-based sintered alloy according to  claim 8 , wherein the ferrous powder is formed into the base of the wear-resistant iron-based sintered alloy by sintering. 
     
     
         10 . The wear-resistant iron-based sintered alloy according to  claim 8 , wherein an oxide of yttrium is present at a surface of the wear-resistant iron-based sintered alloy. 
     
     
         11 . A valve seat, formed of the wear-resistant iron-based sintered alloy according to  claim 8 . 
     
     
         12 . A process for manufacturing hard particles,
 the process comprising:
 preparing a melt containing 20 to 40 mass % of molybdenum, 0.5 to 1.0 mass % of carbon, 5 to 30 mass % of nickel, 1 to 10 mass % of manganese, 1 to 10 mass % of chromium, 5 to 30 mass % of cobalt, 0.05 to 2 mass % of yttrium, and the balance being inadvertent impurities and iron; 
 powderizing the melt; and 
 oxidizing the yttrium. 
   
     
     
         13 . The process according to  claim 12 , wherein the melt is powderized by gas atomization.