Method for inspecting and processing high alloy steels

Abstract

A highly reactive conversion coating chemistry is used during CAVF processing of high hardness steel alloys such as AMS 6509 and AMS 6517 steel alloys. This chemistry produces a hard, thin, black conversion coating that is not fully rubbed off by the media during the CAVF process. Distressed material regions on the surface of the alloys are not susceptible to forming the conversion coating and remain white. Visual inspection for the presence of such regions is facilitated.

1 - 20 . (canceled) 
     
     
         21 . A steel component comprising steel having a surface hardness of greater than 60 HRC and a surface provided with a black conversion coating having a hardness of greater than 5 on the Mohs' hardness scale. 
     
     
         22 . The steel component according to  claim 21 , wherein the conversion coating comprises an oxalate. 
     
     
         23 . The steel component according to  claim 22 , wherein the conversion coating comprises a predominance of iron (III) oxalate. 
     
     
         24 . The steel component according to  claim 21 , wherein the conversion coating has a thickness of between 0.1 microns and 2.0 microns in thickness. 
     
     
         25 . The steel component according to  claim 21 , wherein the surface has a surface roughness Ra of less than 0.25 micron. 
     
     
         26 . The steel component according to  claim 21 , wherein the surface has a surface roughness Ra of less than 0.1 micron. 
     
     
         27 . The steel component according to  claim 21 , wherein the surface has a surface roughness Ra of less than 0.05 micron. 
     
     
         28 . The steel component according to  claim 21 , wherein the component is case hardened to a surface hardness of 62 HRC or higher. 
     
     
         29 . The steel component according to  claim 21 , wherein the steel is AMS 6509 or AMS 6517 alloy steel. 
     
     
         30 . The steel component according  claim 21 , wherein the steel is a steel alloy comprising one or more or all of the following:
 0.1 to 0.15 weight percent carbon   16 to 18 weight percent cobalt,   7.5 to 9.5 percent weight percent nickel,   about 3.5 weight percent chromium,   1.0 to 2.0 weight percent molybdenum,   up to 0.25 weight percent tungsten,   up to 0.02 weight percent vanadium;   
       with the balance being iron. 
     
     
         31 . The steel component according to  claim 21 , wherein the component is a gear, a bearing, a shaft, a journal, a cam, a piston, an axle, a seat or a seal. 
     
     
         32 . The steel component according to  claim 31 , that has been machined by turning, broaching, grinding, skiving or honing, giving rise to grind lines on the surface, which grind lines have been planarised by chemically accelerated vibratory finishing. 
     
     
         33 . The steel component comprising steel having a surface hardness of greater than 60 HRC and a planarized isotropic surface having a surface roughness Ra of less than 0.1 micron. 
     
     
         34 . The steel component according to  claim 33 , wherein the component is a gear. 
     
     
         35 . The steel component according to  claim 33 , wherein the steel is AMS 6509 or AMS 6517 alloy steel and the component is case hardened to a surface hardness of 62 HRC or higher. 
     
     
         36 . A method of processing a steel component according to  claim 33 , wherein the component is processed according to a method comprising:
 providing a mass finishing machine having a receptacle containing a quantity of media;   supplying to the receptacle a quantity of an acid based liquid chemical solution for forming a hard black conversion coating;   immersing the component at least partially in the media such that the surface is exposed to the liquid chemical solution whereby an oxalate conversion coating is formed on the surface;   processing the component by inducing movement between the surface and the media thereby forming the oxalate conversion coating on the surface and rubbing it away with the media;   balancing the rubbing action of the media with the formation of the conversion coating to ensure a stable coating of more than 0.1 microns in thickness, whereby etching of the surface of the component is eliminated.   
     
     
         37 . The method according to  claim 36 , comprising continuing the process until a surface roughness of the component Ra is less than 0.1 micron. 
     
     
         38 . The method according to  claim 36 , comprising terminating the processing of the component and subsequently removing the conversion coating. 
     
     
         39 . A liquid chemical solution for use in the method of  claim 36 , comprising:
 0.6 to 10.5 v/v % of oxalic acid;   0.0003 to 1.0 v/v % of sodium thiocyanate;   0 to 3.0 v/v % of sodium metal nitrobenzene sulfonate (SMNBS);   0.0001 to 0.5 v/v % of a surfactant;   
       and the balance being water. 
     
     
         40 . The liquid chemical solution according to  claim 39 , comprising:
 0.8 to 1.2 v/v % of oxalic acid;   0.0005 to 0.002 v/v % of sodium thiocyanate;   0 to 0.02 v/v % of SMNBS;   0.0005 to 0.02 v/v % of the surfactant;   
       and the balance being water.