Research On Surface Thermal Spraying On Enhancing High-temperature Wear Resistance Of H13 Steel

As a commonly used hot die material,no effective way was found to elongate the service life of H13 steel.Thus,to find a spray technique and material for the surface strengthening and repairing,the High Velocity Oxygen Fuel spray process and means of oxyacetylene flame spray-welded process were employed to create Cr₃C₂-NiCr coating and Ni60 A coating on the surface of H13 in this paper.Considering the surface finish,microhardness and shear bond strength of the coating,the microstructures,phase structures and interface adhesion mechanism of all the powder and coating.Also the experiment of thermal fatigue property and high temperature friction and wear behavior on the coating were conducted.The microstructure of two obtained coating is evenly distributed and cohesively bound layer by layer.Cr₃C₂-NiCr coating and the base are mechanically combined,while Ni60 A coating and the base are metallurgically combined.Aside from phases of Cr₃C₂,NiCr which were contained in the coating material of Cr₃C₂-NiCr coating,small amount of Cr7C3,Cr2O3 coexisted due to the burning loss and the oxidation of carbon during spray process.It turned out that there is no big difference between the base and Ni60 A coating which is comprised of γ-（Ni,Cr）,（Fe,Ni）23C6,carbide and boride of Cr,etc.The results show that Cr₃C₂-NiCr coating has the highest microhardness,followed by Ni60 A coating and H13 comes third.While microhardness of Ni60 A coating is more stable than that of the Cr₃C₂-NiCr coating.At room temperature and the temperature of 600℃,shear bond strength between Ni60 A coating and the base is obviously better than Cr₃C₂-NiCr coating,contrary to the thermal fatigue property at the temperature of 400℃ and 600℃.In the high temperature friction and wear behavior experiment at the temperature of 400℃,there is no much difference in the wearing depth between Cr₃C₂-NiCr coating and H13.But with the rise of temperature,high-temperature wear resistance of Cr₃C₂-NiCr coating better than that of H13 evidently.When reaching the temperature of 600℃,the wearing depth of H13 is as twice as much in Cr₃C₂-NiCr coating,yet pretty the same as H13 in 400℃⁶00℃.