Method for manufacturing sintered and carburized porous stainless steel parts

Abstract

This invention presents a method for manufacturing sintered and carburized porous stainless steel parts, comprising steps of: sintering stainless steel powders to obtain a porous sintered stainless steel, wherein the porous sintered stainless steel comprises a three dimensional network skeleton structure with a large number of interconnected pore channels; and carburizing the porous sintered stainless steel by a non-halogenated carbon-bearing gas, wherein the porous sintered stainless steel being maintained at a carburizing temperature below 600° C. such that carbon atoms can be implanted into the porous sintered stainless steel and converts a surface portion of the skeleton structure, that is in contact with the carbon-bearing gas in the interconnected pore channels, into a carburized layer. A carburized layer is formed and spread over a skeleton structure of the sintered porous body. Thereby, the strength, surface hardness, and core hardness of the sintered body are significantly increased.

What is claimed is: 
     
         1 . A method for manufacturing sintered and carburized porous stainless steel parts, comprising steps of:
 Step 1: sintering stainless steel powders under a vacuum or a hydrogen-bearing atmosphere to obtain a porous sintered stainless steel with a relative density at a range between 30% to 89%, wherein the porous sintered stainless steel comprises a three dimensional network skeleton structure with a large number of interconnected pore channels; and   Step 2: carburizing the porous sintered stainless steel by a non-halogenated carbon-bearing gas, wherein the porous sintered stainless steel being maintained at a carburizing temperature below 600° C. such that carbon atoms can be implanted into the porous sintered stainless steel and converts a surface portion of the skeleton structure, that is in contact with the carbon-bearing gas in the interconnected pore channels, into a carburized layer;   wherein there is no activation treatment with halogenated materials is carried out on the porous sintered stainless steel between Step 1 and Step 2.   
     
     
         2 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 1 , wherein the non-halogenated carbon-bearing gas is selected from a group consisted of carbon monoxide, methane, ethylene, acetylene, propane and a mixture thereof. 
     
     
         3 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 1 , wherein the carburizing temperature ranges from 400° C. to 580° C. 
     
     
         4 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 1 , wherein the porous sintered stainless steel is sintered from a green compact that is fabricated with a Metal Injection Molding method. 
     
     
         5 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 1 , wherein the porous sintered stainless steel is sintered from a green compact that is fabricated with a powder-compaction method. 
     
     
         6 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 1 , wherein the porous sintered stainless steel body is sintered from loose powders which are placed in a mold without compaction. 
     
     
         7 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 1 , wherein the porous sintered stainless steel body is sintered from a green compact of a stainless steel powder, which is an iron-based material containing less than 1.0 wt % silicon, less than 2.0 wt % manganese, 8.0-19.0 wt % chromium, less than 15.0 wt % nickel, less than 6.0 wt % molybdenum, and less than 6.0 wt % copper.