Microstructure And Properties Of Mo-Cr-Si Coating For Marine Engine Restoration

Adopting surface technology to nickel base superalloy to acquire metal coating with high-melting-point which can satisfy the needs of high thrust and light weight of turbine engine to the temperature and efficiency of fuel gas jet pipe entrance。Mo-Cr-Si alloy have fine high temperature oxidation resistance, Can effectively reduce the operating temperature of base material, Reduce the thermal shock damage, improve the thermal efficiency and have been widely used in chemical industry, metallurgy, aerospace and energy fields.In this work, Mo-Cr-Si metal coatings were fabricated by Plasma Spraying method with spraying materials of Mo, Cr and Si powder. The phase composition and microstructure of coatings were characterized by XRD and SEM. Furthermore, the micro-hardness, bonding strength, wear resistance, corrosion resistance of the coating before and after arc remelt were also analyzed. The results are shown as follows:(1) Mo-Cr-Si coating prepared by Mo, Cr and Si and a small amount of Mo Si2, Cr3 Si phase, Mo Si2 phase and Cr3 Si phase generated a small amount can improve the performance of high-temperature protective coating further. Mo-Cr-Si coating is uniform and compact, smooth surface, low roughness, good bonding with the base, with no pores and defects on the interface of the coating hardness; the average value is 460.9 HV0.1; the bonding strength of the coating is an average of 61.5MPa.(2) After remelting treatment, with the increasing of Mo content, the more fine grain microstructure appear, and the shape from net becoming flaky and granular, at the same time, precipitation of eutectic metal compounds reduced,. With the increasing of Cr content, the structure refinement, eutectic metal compounds tend to intergranular precipitation, the precipitation amount is increased. With the increasing of Si content, promote the formation of the second phase more strongly, the column shaped precipitates a lot of floc or coarse bar shape, coarse grains generated. Increasing the content of Mo after remelting treatment, the corrosion resistance of Ni based coating decreased. The content of Cr increased, the corrosion resistance of Ni based coating will improve. With the increasing of Si content, because the second phase precipitation amount, will greatly reduce the corrosion resistance of the coating.(3)Hardness and abrasive wear properties of the laser cladding coating increased with the increasing of Cr content, and decreased with the increase of the content of Si. The content of Cr is higher, the better corrosion resistance; When the content of Si is less than 20%, the content of Si can decrease the corrosion resistance of the coating, but the content of Si can improve the corrosion resistance when the content of Si exceeds 20%.