Three step surface enhancement process for carbon alloy fluid ends

Abstract

A method for improving corrosion resistance and fatigue performance of a metallic surface of an article comprises nitrocarburizing the metallic surface to provide a nitrocarburized surface; forming an oxide layer on the nitrocarburized surface; and treating the oxide layer with a mechanical process.

What is claimed is: 
     
         1 . A method for improving corrosion resistance and fatigue performance of a metallic surface of an article, the method comprising:
 nitrocarburizing the metallic surface to provide a nitrocarburized surface;   forming an oxide layer on the nitrocarburized surface; and   treating the metallic surface with a mechanical deformation process after the oxide layer is formed.   
     
     
         2 . The method of  claim 1 , wherein the mechanical process comprises shot peening, laser shock peening, water jet peening, burnishing, cavitation peening, controlled impact peening, pinch peening, or a combination comprising at least one of the foregoing. 
     
     
         3 . The method of  claim 1 , wherein nitrocarburizing comprises heating the metallic surface in a gaseous medium at a temperature of about 800° F. to about 1300° F. 
     
     
         4 . The method of  claim 3 , wherein the gaseous medium comprises ammonia and a carbon source comprising carbon dioxide, carbon monoxide, methanol, methane, ethane, propane, butane, pentane, or a combination comprising at least one of the foregoing. 
     
     
         5 . The method of  claim 4 , wherein the gaseous medium further comprises nitrogen. 
     
     
         6 . The method of  claim 1 , wherein forming an oxide layer comprises oxidizing the nitrocarburized surface with air, steam or warm, moist air for about 1 to about 4 hours at about 400° F. to about 600° F. 
     
     
         7 . The method of  claim 1 , further comprising treating the nitrocarburized surface with a sealant, an oil, or a combination comprising at least one of the foregoing. 
     
     
         8 . The method of  claim 1 , further comprising treating the oxide layer with a sealant, an oil, or a combination comprising at least one of the foregoing. 
     
     
         9 . The method of  claim 1 , wherein the mechanical deformation process comprises shot peening. 
     
     
         10 . The method of  claim 9 , wherein shot peening comprises projecting shot materials onto the metallic surface after the oxide layer is formed, wherein the shot materials comprises metallic particles, glass beads, ceramic materials, or a combination comprising at least one of the foregoing. 
     
     
         11 . The method of  claim 1 , wherein the metallic surface comprises steel. 
     
     
         12 . The method of  claim 1 , wherein the metallic surface comprises carbon steel. 
     
     
         13 . The method of  claim 1 , wherein the article is a piston, plunger, pipe, steel ball, steel ball bearing, a fluid end, or a component of a fluid end assembly. 
     
     
         14 . An article comprising a treated metallic surface, the treated metallic surface comprising:
 a diffusion layer and a compound layer from a nitrocarburization process, and   an oxide layer from an oxidization process;   wherein a compression stress layer and a tensile stress layer from a mechanical deformation process are present in the treated metallic surface.   
     
     
         15 . The article of  claim 14 , wherein the diffusion layer has a thickness of greater than about 100 microns. 
     
     
         16 . The article of  claim 14 , wherein the compound layer has a thickness of about 5 to about 25 microns. 
     
     
         17 . The article of  claim 14 , wherein the oxide layer has a thickness of about 0.2 to about 2 microns. 
     
     
         18 . The article of  claim 14 , wherein the treated metallic surface further comprises at least one of a sealant or an oil. 
     
     
         19 . The article of  claim 14 , wherein the article is a piston, plunger, pipe, steel ball, steel ball bearing, a fluid end, or a component of a fluid end assembly. 
     
     
         20 . An article comprising a surface treated according to the process of  claim 1 .