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 . A production method for an iron-based sintered alloy material comprising:
 molding an iron-based mixed powder comprising 0.1 to 1.2% by mass of a graphite powder and 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 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 590° to 900° C. in an atmosphere comprising ammonia,   subjecting the iron-based sintered alloy substrate that has undergone the nitriding treatment to a quenching treatment with rapid cooling from a quenching temperature that is a temperature of 640 to 800° C. and is lower than the nitriding temperature, and   subjecting the iron-based sintered alloy substrate that has undergone the quenching treatment to tempering by heating at 100 to 200° C.   
     
     
         2 . The production method for an iron-based sintered alloy material according to  claim 1 , wherein the quenching is conducted by reducing a temperature from the nitriding temperature to the quenching temperature at a temperature reduction rate of 0.6 to 1.0° C./min, and rapidly cooling from the quenching temperature. 
     
     
         3 . The production method for an iron-based sintered alloy material according to  claim 1 , wherein the tempering after the quenching is performed by heating the substrate at 150 to 200° C. 
     
     
         4 . The production method for an iron-based sintered alloy material according to  claim 1 , wherein the nitriding treatment is performed at the nitriding temperature for 120 to 180 minutes. 
     
     
         5 . The production method for an iron-based sintered alloy material according to  claim 1 , wherein the at least one alloying component comprises 0.15 to 4.5% by mass of chromium. 
     
     
         6 . The production method for an iron-based sintered alloy material according to  claim 1 , wherein the at least one alloying component comprises 0.2 to 4.5% by mass of copper. 
     
     
         7 . An iron-based sintered alloy material obtainable by the production method for an iron-based sintered alloy material according to  claim 1 .