Surface Modification by HVOF Coating of Micron-Sized WC-Metal Powder and Laser-Heating of the Coating

μWC-metal powder (powder) was coated onto the surface of Inconel 718 (IN718) using HVOF spraying for the improvement of surface properties. The coating was heat-treated by CO2(g) laser for further improvement of the properties. Optimal coating process was obtained from surface properties of 9 coatings prepared by Taguchi program. Surface property improvement by HVOF coating and laser-heating were investigated. The surface hardness of IN718 was increased by coating from 399 Hv to 1260±30 Hv, and further increased to 1860±100 Hv by laser-heating. Porosity of the coating was decreased by laser-heating from 2.2±0.3% to 0.4±0.1%. The friction coefficient of the surface was decreased by the coating from 0.48±0.06 to 0.33±0.02 at room temperature. Friction coefficients of IN718 and the coating were decreased with increasing sliding surface temperatures from 25°C to 450°C. According to reciprocating sliding wear tests, wear depth and trace of the coating were smaller than IN718 at both 25°C and 450°C. The coating had better wear resistance compared to IN718, creating smaller wear traces. At 450°C, wear depth of coating was much smaller than IN718: 50-µm-deep groove compared to 75 µm for IN718.