Research Of Reinforcement On Mould's Surface

The Ni-based and Co-based alloy coating with flame spray welding and plasma surfacing are studied in this paper in order to solve the surface corrosion and wear problem of the mould. Through the ways of SEM, XRD, etc, the microstructure of samples are researched. And the wear, corrosion resistance and heat-resistant properties of coating are analyzed.The way of the NiWC35 and NiWC50 alloy with flame spray welding on the 45 steel mould surface, and the way of the CoWC50 alloy with plasma surfacing on the 45, 40Cr, Cr12MoV steel mould surface are used. The coating microstructure, component, wear resistance, corrosion resistance and heat-resistant properties are analyzed in this paper. The result shows that the self-fluxing Ni-based and Cobalt-based alloy possesses excellent capability of bearing high temperature, better heat strength, better corrosion resistance and thermal fatigue properties. This kind of alloy can be used as the coating of the parts which are needed to be oxidation resistant, wear and corrosion resistant. It can be used in the surfacing reinforce technology such as the coating of the oscillating rolling dies and other hot dies. Because the price of 45, 40Cr and Cr12MoV steel are low, the study uses the ordinary material, which takes the place of the high-value high alloy mould steel.The hardness and wear resistance of the coating are higher than that of the substrate. Because the large numbers of the white and bright tiny particles exist in the coating have the regular geometry and they are carbides. The carbides in the coating are fine and tiny which play a very important part to enforce the hardness and wear resistance of the coating. The microstructure of the coating is uniform. Because of the effective diffusion, after the alloy melting, each element diffused each other and then after the solidification the metallurgical bond was formed excellently between the coating and the substrate. The coating hardness, strength and toughness, wear resistance were better. The alloy elements in the solid solution play part in the hardening for one hand. And on the other hand being the hard phase in the solid solution, it works as the second-phase hardening especially when the carbide migrating which improved the effect of the second-phase hardening seriously. The plasma surfacing and flame spray welding have lower rate of dilution and the lower hardness substrate has little effects to the coating. These make the alloy forming the hard compound without being diluted. And the hard compounds working as the framework in the surfacing coating improve the hardness of it. In addition, the result shows that the coating corrosion resistance are higher than that of the substrate. The coating was formed by the tiny dendritic and the fine carbides among them and the co-crystallizations. We can also know that the components of the surface are uniform and the grain-oriented is similar. So the galvanic cell effects formed by the different orientation of the grains slow down the corrosion. At the same time, the surfacing improved the alloy element solid solubility, suppressed or decreased greatly the x-phase,α-phase and the carbide separating out. And it reduced the tendency of the corrosion.