Laser Duplex Treatment of Surfaces for Improved Properties

Laser treatment of surfaces finds wide applications in industry due to its advantages over the conventional techniques such as meeting required surface quality, short processing time, precision of operation, local treatment, and low cost. Laser surface processing can be extended to include duplex treatment, in which case, treated surfaces can be scanned by a laser beam for further improvement of the tribological properties. One of the examples for the duplex treatment is that the compound layer is formed at the plasma-nitrided surfaces, which is hard and brittle. The life cycle of the surface is short under the fatigue or abrasive wear loads. Laser-controlled melting offers solution to this problem through mixing the compound layer with the underlying material while improving the fracture toughness at the surface with small decrease in hardness. In addition, laser gas-assisted processing enables to form nitride and/or carbonitride species at the surface when the workpiece surface is treated prior to the laser scanning. In this case, diamondlike surfaces can be generated and the surface hardness and fracture toughness can be improved significantly. Laser-controlled melting involves phase change at the surface and the depth of melt penetration depends on the processing parameters. In order to achieve defect-free treated surfaces, proper selection of the laser treatment parameters is necessary. Analytical and numerical treatment of the phase change preprocess minimizes the experimental efforts to identify the levels of the affecting parameters. Consequently, in this chapter, the fundamentals of laser duplex treatment of surfaces are introduced and model studies in relation to parametric analysis of the affecting parameters are presented. The experimental data pertinent to the cases involving laser duplex treatment are included and discussions for the findings are presented in detail.