Composite Sintered Compact And Method For Producing Composite Sintered Compact

Abstract

A composite sintered compact containing: a first portion composed of a sintered compact of a first stainless steel, a second portion composed of a sintered compact of a second stainless steel a steel type of which is different from that of the first stainless steel, the second portion being diffusion-bonded to the first portion at an interface, wherein a surface on which the first portion is exposed is defined as a first surface, a surface on which the second portion is exposed is defined as a second surface, a step between the first surface and the second surface is 100 μm or less, and a difference between the light reflectance of the first surface during polishing and the light reflectance of the second surface during polishing is 2% or greater.

What is claimed is: 
     
         1 . A composite sintered compact comprising:
 a first portion composed of a sintered compact of a first stainless steel,   a second portion composed of a sintered compact of a second stainless steel a steel type of which is different from that of the first stainless steel, the second portion being diffusion-bonded to the first portion at an interface thereof, wherein   provided that a surface where the first portion is exposed is defined as a first surface, and   a surface where the second portion is exposed is defined as a second surface,   a step between the first surface and the second surface is 100 μm or less, and   a difference between the light reflectance of the first surface during polishing and the light reflectance of the second surface during polishing is 2% or greater.   
     
     
         2 . The composite sintered compact according to  claim 1 , wherein a difference between the Vickers hardness of the first surface and the Vickers hardness of the second surface is 300 or less. 
     
     
         3 . The composite sintered compact according to  claim 1 , wherein
 the first stainless steel is an austenitic stainless steel containing Fe, Ni, and Mo,   the second stainless steel is a precipitation hardening stainless steel containing Fe, Ni, and Cu,   Mo is diffused in a width of from 5 μm to 200 μm across the interface, and   Cu is diffused in a width of from 10 μm to 300 μm across the interface.   
     
     
         4 . The composite sintered compact according to  claim 1 , wherein |Ra−Rb| is 10% or less when the first surface and the second surface are subjected to a re-polishing at a polishing amount of 100 μm,
 Ra being the light reflectance of the first surface before the re-polishing, and 
 Rb being the light reflectance of the first surface after the re-polishing. 
 
     
     
         5 . The method for producing a composite sintered compact according to  claim 1 , comprising:
 a molding step of subjecting a first composition containing a first powder composed of the first stainless steel and a second composition containing a second powder composed of the second stainless steel to multicolor molding to obtain a multicolor molded object, and   a sintering step of subjecting the multicolor molded object to sintering to obtain a composite sintered compact, wherein   a temperature difference between a shrinkage starting temperature of the first powder and a shrinkage starting temperature of the second powder is 50° C. or less.