Research on laser melting-alloying combined strengthening of the camshaft of air-cooled diesel engine

This paper reported the research results on 3 kw cw CO2 laser melting-alloying combined strengthening of the camshaft of air-cooled diesel engine used in the desert oil field. The 45 steel camshaft was pretreated with the conventional quenching and high temperature tempering. A focused laser beam with power density 1.5 - 1.7 X 104 w/cm2 was used to alloy the cam lobe area, while the other area of the cam was treated by laser melting using a focused 12 X 1.5 mm rectangular beam (power density 1.1 X 104 w/cm2) produced by a newly developed binary optics. The microstructure of the laser alloyed region is fine Fe-Cr-Si-B multi-element hypereutectic structure with hardness HRC 63 - 64. The melted layer consists of fine needle-shaped martensite and residual austenite structure with hardness HRC 58 - 61. The strengthened layer is 1.0 - 1.3 mm in thickness with pore-free and crack-free and good surface quality. Under the same condition, the Ring-block (SiN ceramic) wear test proves that the wear of the laser alloyed 45 steel ring is only 29 percent of that of induction quenching 45 steel ring. And a 500 hours test engine experiment demonstrates that the average wear of the laser alloyed cam is only 20 percent of that of induction quenched one.