In order to improve the wear and corrosion resistance of an AZ91D magnesium alloy substrate, an Al_0.5CoCrCuFeNi high-entropy alloy coating was successfully prepared on an AZ91D magnesium alloy surface by laser cladding using mixed elemental powders. Optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction were used to characterize the microstructure of the coating. The wear resistance and corrosion resistance of the coating were evaluated by dry sliding wear and potentiodynamic polarization curve test methods, respectively. The results show that the coating was composed of a simple FCC solid solution phase with a microhardness about 3.7 times higher than that of the AZ91D matrix and even higher than that of the same high-entropy alloy prepared by an arc melting method. The coating had better wear resistance than the AZ91D matrix, and the wear rate was about 2.5 times lower than that of the AZ91D matrix. Moreover, the main wear mechanisms of the coating and the AZ91D matrix were different. The former was abrasive wear and the latter was adhesive wear. The corrosion resistance of the coating was also better than that of the AZ91D matrix because the corrosion potential of the former was more positive and the corrosion current was smaller.

The Cu_0·9NiAlCoCrFe high entropy alloy coating fabricated on AZ91D magnesium alloys by laser cladding is studied in this paper. Microstructure property of the coating is characterised by optical microscope, scanning electron microscope and X-ray diffraction (XRD). The XRD results show that the coating mainly consists of a simple bcc solid solution phase. Corrosion resistance results of the coating are tested in 3·5 wt-%NaCl solution. Compared to the AZ91D specimen without Cu_0·9NiAlCoCrFe coating, the corrosion current density of AZ91D specimen coated with Cu_0·9NiAlCoCrFe decreased by four orders of magnitude.

In order to improve the high temperature oxidation and ablation resistance of C/C composites, ZrB₂-ZrC-SiC ultra-high temperature composite ceramic coatings were prepared on C/C composites by laser cladding using Zr, B₄C, and Si as raw materials. The microstructure of the coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Air isothermal oxidation (1600 °C, 80 min) and oxyacetylene flame ablation (2400 kW/m², 300 s) were used to evaluate the high-temperature oxidation and ablation properties of the coating, respectively. The results show that the microstructure of laser cladding coating is a totem of black and white. The white part is mainly the first solidified high melting point ZrB₂ phase, and the black part is the latter solidified eutectic structure, which is mainly composed of ZrB₂(ZrB₁₂)-ZrC or ZrB₂(ZrB₁₂)-SiC two phases. After oxidation at 1600 °C and 80 min, the coating is mainly composed of ZrO₂ and ZrSiO₄ phases, and ZrSiO₄ is basically distributed among ZrO₂ particles. The high temperature oxidation and ablation properties of the coating are better than the C/C composite matrix, and the mass ablation rate of the coating is about 1/4 of the latter.

In order to improve the wear resistance of titanium alloy, a Ti₅Si₃/Ti₃Al composite coating with improved wear resistance was successfully prepared by laser cladding TA2 titanium alloy using the double-layer presetting method of Ti-63 wt.% Al mixed powder layer/Si powder layer. The microstructure, phase composition and wear resistance of the coating were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and pin-disk friction and wear method. The results show that the coating is mainly composed of the Ti₅Si₃ primary phase and Ti₅Si₃/Ti₃Al eutectic structure. The microhardness of the coating is higher than that of the matrix. The average microhardness of the coating is about 668 HV_0.1, which is 3.34 times that of the matrix. The coating significantly improves the wear resistance of the TA2 matrix, and the mass wear rate is 1/5.79 of that of the TA2 matrix. The main wear mechanisms of the coating are abrasive wear, adhesive wear and oxidative wear, whereas the main wear mechanisms of the TA2 matrix are adhesive wear and oxidative wear.