Sintered and carburized porous stainless steel part and method thereof

Abstract

This invention presents a sintered and carburized porous stainless steel part with improved strength and hardness and method thereof. The sintered and carburized porous stainless steel part has a porous body with a relative density between 30% and 89%, which is sintered from a stainless steel powder, wherein exposed pore surfaces inside the porous body are carburized without forming carbides and without using an activation process in advance. A carburized layer is formed and spread into the core 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 sintered porous stainless steel part with high apparent hardness and strength, comprising a porous body and with a relative density at a range between 30% and 89%, which is sintered from a stainless steel powder, wherein exposed pore surfaces inside the porous body are carburized without forming carbides and without using any activation process with halogenated materials in advance. 
     
     
         2 . The sintered porous stainless steel part according to  claim 1 , wherein the stainless steel powder 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. 
     
     
         3 . A method for manufacturing sintered and carburized porous stainless steel parts, comprising steps of:
 fabricating a sintered stainless steel body, wherein the sintered stainless steel body comprises a porous body and has a relative density at a range between 30% to 89%; and   carburizing the sintered porous stainless steel body directly by a non-halogenated carbon-bearing gas, without any activation process in advance, wherein the sintered stainless steel body being maintained at a carburizing temperature below 600° C. such that carbon atoms can be implanted into exposed pore surfaces and form carburized layers inside the porous body.   
     
     
         4 . The method for manufacturing sintered porous stainless steel parts according to  claim 3 , wherein the non-halogenated carbon-bearing gas is selected from a group consisted of carbon monoxide, methane, ethylene, acetylene, propane and a mixture thereof. 
     
     
         5 . The method for manufacturing sintered porous stainless steel parts according to  claim 3 , wherein the sintered stainless steel body is sintered under a vacuum or a hydrogen-bearing atmosphere. 
     
     
         6 . The method for manufacturing sintered porous stainless steel parts according to  claim 3 , wherein the carburizing temperature ranges from 400° C. to 580° C. 
     
     
         7 . The method for manufacturing sintered porous stainless steel parts according to  claim 3 , wherein the sintered stainless steel body is sintered from a green compact that is fabricated with a Metal Injection Molding method. 
     
     
         8 . The method for manufacturing sintered porous stainless steel parts according to  claim 3 , wherein the sintered stainless steel body is sintered from a green compact that is fabricated with a powder-compaction method. 
     
     
         9 . The method for manufacturing sintered porous stainless steel parts according to  claim 3 , wherein the sintered stainless steel body is sintered from loose powders which are placed in a mold without compaction. 
     
     
         10 . The method for manufacturing sintered and carburized porous stainless steel parts according to  claim 3 , wherein the 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.