az91d镁合金表面激光熔覆al al2o3涂层研究word格式论文.docxVIP

优秀毕业论文 精品参考文献资料 Abstract In this article, we have carried out laser cladding experiments of Al with different weight percentage of Al2O3 composite powders on the surface of AZ91D magnesium alloy substrate through a 3kW crosscurrent type of CO2 laser apparatus. A proper material system and laser cladding parameters were ascertained by the comparison of analyses basing on the microscopic and macroscopic qualities of different cladding layers. By the means of OM, SEM, XRD EDS, etc. different layers phase constitution and microstructure were observed and analyzed, the mechanism of Al2O3 enforcement was also expatiated: Through a kind of disc-pin tribological wear experiment machine, we carried out tribological wear riments on the surface of AZ91D and Al2O3 with different weight percentage of composite coatings, tribological wear mechanism was also discussed basing on tribological wear configuration of variant wear experiment samples. Experiments of laser cladding samples, and the erosion mechanism were discussed too. In the end, we made some useful discussion of different cladding layers corrosion behavior by the way of loss curves. Laser cladding parameters have great effect on microstructure, macro-configuration and the capability of the cladding layers. Under the cladding parameters of P=1.5kW, ν = 800mm/min, D=3mm, we obtained cladding coatings with good surface quality, fine microstructure, low dilution, high microhardness and good metallurgical combination interface with AZ91D substrate. The microstructure analysis results showed that, from the surface of the cladding specimen to the substrate, there are three distinct areas: the cladding area, the bonding area and the heat-affected area in the substrate. The different solidification character parameters it takes on different microstructure in the cladding layers. The typical microstructure was the typical extension growth on the plane basis at the bottom of the layers, cellular crystals near the bonding area,