Surface modification by HVOF coating of micron-sized WC-metal powder and laser-heating of the coating

mu WC-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 degrees C to 450 degrees C. According to reciprocating sliding wear tests, wear depth and trace of the coating were smaller than IN718 at both 25 degrees C and 450 degrees C. The coating had better wear resistance compared to IN718, creating smaller wear traces. At 450 degrees C, wear depth of coating was much smaller than IN718: 50-mu m-deep groove compared to 75 mu m for IN718.