Laser nitriding method of making phosphor bronze with surface-embedded titanium carbide particles

Abstract

The laser nitriding method of making phosphor bronze with surface-embedded titanium carbide particles involves coating a cleaned phosphor bronze workpiece with a thin film formed of a carbonaceous layer mixed with nanosize particles of titanium carbide. The titanium carbide forms about 5 wt % of the thin film, and the phosphor bronze workpiece is composed of about 6.0 wt % tin, about 0.1 wt % phosphorous, and about 93.9 wt % copper. A laser beam is then scanned over the thin film formed on the phosphor bronze workpiece. Coaxially and simultaneously with the laser beam, a stream of nitrogen gas is sprayed on the thin film formed on the phosphor bronze workpiece in order to provide the workpiece with a nitride coating having nanoparticles of titanium carbide embedded therein.

We claim: 
     
         1 . A method of making phosphor bronze with surface-embedded titanium carbide particles, comprising the steps of:
 coating a phosphor bronze workpiece with a layer of water-soluble phenolic resin homogeneously mixed with particles of titanium carbide;   heating the water-soluble phenolic resin homogeneously mixed with the particles of titanium carbide to produce a thin film of carbonaceous material having nanometer-sized particles of titanium carbide formed on the phosphor bronze workpiece;   scanning a laser beam over a surface of the phosphor bronze workpiece having the thin film of carbonaceous material containing nanometer-size particles of titanium carbide formed thereon; and   spraying a stream of nitrogen gas on the thin film formed on the phosphor bronze workpiece coaxially and simultaneously with the laser beam to provide the workpiece with a nitride coating having particles of titanium carbide embedded therein, wherein the titanium carbide comprises 5 wt % of the coating.   
     
     
         2 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , wherein the particles of titanium carbide have a mean particle size of about 400 nm. 
     
     
         3 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , wherein the coating step is performed under a pressure of about 8 bars at a constant temperature of about 175° C. for a period of about two hours. 
     
     
         4 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , wherein the layer has a thickness of about 50 μm. 
     
     
         5 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , wherein the step of heating the water-soluble phenolic resin homogeneously mixed with the powdered titanium carbide is performed in an argon atmosphere at a temperature of about 400° C. 
     
     
         6 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , where said scanning step is performed using a carbon dioxide laser. 
     
     
         7 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 6 , wherein said scanning step comprises generating the laser beam with a power output of about 90 W. 
     
     
         8 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , wherein said spraying step comprises spraying nitrogen gas having a pressure of about 600 kPa. 
     
     
         9 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 1 , wherein the step of scanning the laser beam over the thin film comprises scanning the laser beam at a rate of about 10 cm/s. 
     
     
         10 . A method of making phosphor bronze with surface-embedded titanium carbide particles, comprising the steps of:
 scanning a laser beam over a surface of a phosphor bronze workpiece having a thin film of carbonaceous material containing nanometer-size particles of titanium carbide formed thereon, the phosphor bronze workpiece containing about 6.0% tin, about 0.1 wt % phosphorous, and about 93.9 wt % copper, the thin film of carbonaceous material containing about 5 wt % titanium carbide particles; and   spraying a stream of nitrogen gas on the thin film formed on the phosphor bronze workpiece coaxially and simultaneously with the laser beam to provide the workpiece with a to nitride coating having particles of titanium carbide embedded therein.   
     
     
         11 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 10 , wherein the particles of titanium carbide have a mean particle size of about 400 nm. 
     
     
         12 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 11 , wherein the thin film has a thickness of about 50 μm. 
     
     
         13 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 10 , wherein the scanning step further comprises generating the laser beam with a carbon dioxide laser. 
     
     
         14 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 13 , wherein said step of generating the laser beam with the carbon dioxide laser comprises generating the laser beam with a power output of about 90 W. 
     
     
         15 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 10 , wherein the step of spraying the stream of nitrogen gas on the thin film coaxially and simultaneously with the laser beam comprises spraying nitrogen gas at a pressure of about 600 kPa. 
     
     
         16 . The method of making phosphor bronze with surface-embedded titanium carbide particles as recited in  claim 12 , wherein the step of scanning the laser beam over the thin film comprises scanning the laser beam at a rate of about 10 cm/s.