THREE STEP SURFACE ENHANCEMENT PROCESS FOR CARBON ALLOY FLUID ENDS
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.
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 .