Method Of Manufacturing A Ferrous Alloy Article Using Powder Metallurgy Processing

Abstract

A method of manufacturing a ferrous alloy article is disclosed and includes the steps of melting a ferrous alloy composition into a liquid, atomizing and solidifying the liquid into powder particles, removing oxygen from surfaces of the powder particles to reduce a bulk oxygen content to approximately ≤20 ppm, and consolidating the powder particles into a monolithic article.

What is claimed is: 
     
         1 . A method of manufacturing a ferrous alloy article, comprising the steps of:
 melting a ferrous alloy composition into a liquid;   atomizing and solidifying the liquid into powder particles;   removing oxygen from surfaces of the powder particles to reduce a bulk oxygen content to approximately ≤20 ppm; and   consolidating the powder particles into a monolithic article.   
     
     
         2 . The method of  claim 1 , wherein the step of consolidating the powder particles is performed using hot isostatic pressing (HIP). 
     
     
         3 . The method of  claim 2 , wherein outgassing is performed through vacuum hot gassing the powder particles positioned in a container. 
     
     
         4 . The method of  claim 3 , wherein atomization is performed using a high pressure inert gas. 
     
     
         5 . The method of  claim 4 , wherein the high pressure inert gas is Nitrogen. 
     
     
         6 . The method of  claim 4 , wherein the high pressure inert gas is Argon. 
     
     
         7 . The method of  claim 3 , wherein the monolithic article is consolidated from the powder particles in a container. 
     
     
         8 . The method of  claim 1 , further comprising the step of separating the powder particles by size. 
     
     
         9 . The method of  claim 8 , wherein the separated powder particles are mixed into a homogenized blend. 
     
     
         10 . The method of  claim 1 , further comprising the step of screening the powder particles using a mesh. 
     
     
         11 . The method of  claim 10 , wherein the separated powder particles are mixed into a homogenized blend. 
     
     
         12 . The method of  claim 1 , wherein removal of the oxygen is performed through vacuum hot outgassing to remove oxides from the surface of the powder particles. 
     
     
         13 . The method of  claim 12 , wherein outgassing reduces a bulk oxygen content of a resulting consolidated product to approximately ≤20 ppm. 
     
     
         14 . The method of  claim 13 , wherein outgassing reduces a bulk oxygen content of a resulting consolidated product to approximately ≤10 ppm 
     
     
         15 . The method of  claim 1 , further comprising the step of filing a container with the powder particles. 
     
     
         16 . The method of  claim 1 , further comprising the step of forging the monolithic article. 
     
     
         17 . The method of  claim 1 , further comprising the step of hot working the monolithic article. 
     
     
         18 . The method of  claim 1 , wherein the ferrous alloy composition includes, in wt. % of, about:
 C 0.2-0.5 Mn 0.1-1.0 Si 0.1-1.2 Cr 9-14.5 Ni 3.0-5.5 Mo 1-2 Cu up to 1.0 Co 1-4 V 0.1-1.0 Ti up to 0.5 the balance of the ferrous alloy being iron and usual impurities including not more than about 0.01% phosphorus and not more than about 0.002% sulfur.   
     
     
         19 . The method of  claim 18 , wherein the ferrous alloy composition includes, in wt. % of, about:
 C 0.35-0.45 Mn 0.1-0.7 Si 0.1-1.0 Cr 9.5-12.5 Ni 3.2-4.3 Mo 1.25-1.75 Cu 0.1-1.0 Co 2-3 V 0.3-0.6 Ti up to 0.2 the balance being iron and the usual impurities including not more than about 0.005% phosphorus and not more than about 0.0005% sulfur.