Iron-based sintered alloy material and production method therefor

Abstract

An iron-based sintered alloy material having, at the surface of the material, a hardened layer exhibiting a martensite phase containing a solid solution of nitrogen in a supersaturated state. The iron-based sintered alloy material may contain at least one of chromium, copper, molybdenum, manganese and nickel. A production method for the iron-based sintered alloy material includes: subjecting an iron-based sintered alloy substrate containing carbon to a nitriding treatment by heating the substrate to a nitriding temperature of at least 590° C. in an atmosphere containing ammonia, and then performing quenching by rapidly cooling the substrate.

1 . An iron-based sintered alloy material comprising carbon and having, at a surface of the material, a hardened layer exhibiting a martensite phase containing a solid solution of nitrogen in a supersaturated state. 
     
     
         2 . The iron-based sintered alloy material according to  claim 1 , comprising 0.1 to 1.0% by mass of carbon. 
     
     
         3 . The iron-based sintered alloy material according to  claim 1 , further comprising at least one alloying component selected from the group consisting of chromium, copper, molybdenum, manganese and nickel. 
     
     
         4 . The iron-based sintered alloy material according to  claim 1 , further comprising at least one alloying component selected from the group consisting of 0.15 to 4.5% by mass of chromium, 0.2 to 4.5% by mass of copper, 0.1 to 2.0% by mass of molybdenum, 0.1 to 3.0% by mass of manganese, and 0.2 to 4.5% by mass of nickel. 
     
     
         5 . The iron-based sintered alloy material according to  claim 1 , wherein the hardened layer has a depth of at least 100 μm from the surface of the material. 
     
     
         6 . A production method for an iron-based sintered alloy material comprising:
 molding an iron-based mixed powder comprising a carbon powder into a green compact of a desired shape,   obtaining an iron-based sintered alloy substrate by heating and sintering the green compact at 1,000 to 1,300° C. in a non-oxidizing environment,   performing a nitriding treatment by heating the iron-based sintered alloy substrate to a nitriding temperature of at least 590° C. in an atmosphere comprising ammonia, and subjecting the iron-based sintered alloy substrate that has undergone the nitriding treatment to rapid cooling and quenching.   
     
     
         7 . The production method for an iron-based sintered alloy material according to  claim 6 , wherein the quenching is conducted at a quenching temperature that is lower than the nitriding temperature. 
     
     
         8 . The production method for an iron-based sintered alloy material according to  claim 6 , wherein following the quenching, tempering is performed by heating the substrate at 100 to 200° C. 
     
     
         9 . The production method for an iron-based sintered alloy material according to  claim 6 , wherein the carbon powder contained in the iron-based mixed powder is 0.1 to 1.2% by mass of a graphite powder. 
     
     
         10 . The production method for an iron-based sintered alloy material according to  claim 6 , wherein the iron-based mixed powder further comprises at least one alloying component selected from the group consisting of chromium, copper, molybdenum, manganese and nickel. 
     
     
         11 . The production method for an iron-based sintered alloy material according to  claim 6 , wherein the iron-based mixed powder further comprises at least one alloying component selected from the group consisting of 0.15 to 4.5% by mass of chromium, 0.2 to 4.5% by mass of copper, 0.1 to 2.0% by mass of molybdenum, 0.1 to 3.0% by mass of manganese, and 0.2 to 4.5% by mass of nickel.