Friction And Wear Behaviors And High-temperature Oxidation Resistance Of In-situ TiC Particle Reinforced Cladding Coating

In-situ TiC particle reinforced composite coating which is based on the chemical reaction between Ti and C3C2under the high temperature is synthesized on H13steel surface by6kW transverse flow CO2laser device. The phase composition, microstructure, Vickers hardness, friction and wear behavior and high temperature oxidation resistance of the composite coating are analyzed using X-ray diffraction (XRD), energy dispersive spectrum (EDS), optical microscope (OM), scanning electron microscopy (SEM), Vickers hardness gage, friction and wear testing machine and muffle furnace. The microstructure and mechanical properties of composite coating was analysized, aiming to provide theoretical basis for the damaged surface of H13steel hot forging die repaired by laser cladding technique.XRD phase analysis results indicate that the coating is composed of TiC, Cr7C3and Fe-Cr phase with the molar ratio of Ti to Cr3C2is2.44:1. With the decreasing of the Ti power content, the increasing of Cr3C2power content, Cr7C3phase increase in the coating which the molar ratio of Ti to Cr3C2is2:1,(Cr, Fe)7C3phase is found in the coating which the molar ratio of Ti to Cr3C2is2:2.33. OM analysis show that three kinds of powder ratio of cladding layer present good metallurgical bonding with the substrate, there are porosity and crack defects in bonding interface. The grain is very fine and dense in coating surfaces and is bulky dendrite in the bonding zone.SEM and EDS analysis show that the morphology of TiC phase gradually shift from ball to lamellar with the increasing of the laser power density.When the molar ratio of Ti to Cr3C2is2:2.33and the laser power density is24.38kW·cm-2, the macro-morphology of surface coating is best, no pores and cracks appear. The highest average micro-hardness of the composite coating is931.9HV0.2, which is about2.21times higher than that of the substrate. The wear resistant of the composite coating are significantly improved, the finally wear loss is only27.2%of the substrate and relative wear resistance is3.68times of the substrate at room temperature. The finally wear loss is only26.4%of the substrate and relative wear resistance is3.79times of the substrate at high-temperature700℃。 At800℃oxidation13h condition, the oxidation product of composite coatings are Cr2O3and TiO2, the oxidation product of H13steel are (Feo.6Cro.4)203and Fe2O3. The oxidation mass gain and oxidation rate of composite coatings are very slower, the relative oxidation resistance are better than that of H13steel, the highest value of the relative oxidation resistance is9.62.