Lubricated low temperature carburized stainless steel parts

Abstract

The surfaces of a stainless steel part are made harder without sacrificing corrosion resistance by subjecting the part to low temperature carburization. The soot layer formed as a by-product of carburization is then removed without removing the non-coherent metal oxide layer which also forms as a by-product. A solid lubricant is then applied to reduce the coefficient of friction of the carburized surface. The by-product metal oxide layer acts as an anchor keeping the solid lubricant in place.

We claim:  
     
         1 . A stainless steel part having at least one carburized surface substantially free of carbide precipitates, the part further comprising an metal oxide layer on the carburized surface and a solid lubricant on the metal oxide layer.  
     
     
         2 . The stainless steel part of  claim 1 , wherein the metal oxide layer is a by-product of the carburization reaction used for forming the carburized surface substantially free of carbide precipitates.  
     
     
         3 . The stainless steel part of  claim 1 , wherein the solid lubricant is graphite, molybdenum disulfide, tungsten disulfide, ultra high molecular weight polyethylene or a halogenated polymer.  
     
     
         4 . The stainless steel part of  claim 1 , wherein the solid lubricant is particulate in form and includes a binder.  
     
     
         5 . The stainless steel part of  claim 1 , wherein the carburized surface is a bearing surface.  
     
     
         6 . The stainless steel part of  claim 5 , wherein the part is a nut.  
     
     
         7 . The stainless steel part of  claim 1 , wherein the stainless steel is substantially or partially austenite.  
     
     
         8 . The stainless steel part of  claim 7 , wherein the stainless steel is AISI 316, 316L, 317, 317L and 304 stainless steels, alloy 600, alloy C-276 and alloy-20 Cb, Nitronic alloy, alloy-58, alloy-825, alloy-254 SmO.  
     
     
         9 . A process for enhancing the slipperiness of the carburized surface of a stainless steel part, the carburized surface being produced by low temperature carburization whereby the carburized surface is substantially free of carbide precipitates, the process comprising coating the metal oxide layer produced as a by-product of carburization with a solid lubricant.  
     
     
         10 . The process of  claim 9 , wherein a soot layer on the metal oxide layer is also formed as a by-product of carburization, the process further including removing the soot layer without substantially removing the metal oxide layer before application of the solid lubricant.  
     
     
         11 . The process of  claim 9 , wherein the stainless steel is substantially or partially austenite.  
     
     
         12 . The process of  claim 11 , wherein the stainless steel is AISI 316, 316L, 317, 317L and 304 stainless steels, alloy 600, alloy C-276 and alloy-20 Cb, Nitronic alloy, alloy-58, alloy-825, alloy-254 SmO.  
     
     
         13 . The process of  claim 9 , wherein the solid lubricant is graphite, molybdenum disulfide, tungsten disulfide, ultra high molecular weight polyethylene or a halogenated polymer.  
     
     
         14 . The process of  claim 9 , wherein the solid lubricant is particulate in form and includes a binder.  
     
     
         15 . The process of  claim 9 , wherein the carburized surface is a bearing surface.  
     
     
         16 . A stainless steel part having at least one carburized surface substantially free of carbide precipitates, the part further comprising an adherent, non-coherent metal oxide layer on the carburized surface and a solid lubricant on the metal oxide layer.