7075铝合金表面激光熔覆Ti/TiBCN复合涂层的组织及性能

摘要

采用激光熔覆技术在7075铝合金表面制备了Ti/TiBCN复合涂层,研究了工艺参数对复合涂层的微观组织及性能的影响.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)研究了Ti/TiBCN复合涂层的相组成和微观组织;利用显微维氏硬度计和往复摩擦磨损试验机研究了Ti/TiBCN涂层的性能.结果表明:当激光功率1 000W,扫描速度3 mm/s,送粉率300 mg/min时,Ti/TiBCN复合涂层质量最好.涂层上部由树枝晶和部分胞状晶组成,涂层中部为等轴晶,涂层下部呈现球形的TiBCN颗粒.与铝合金基体相比,涂层的平均硬度为519.4 HV0.2,是基体(～120 HV0.2)的4.3倍;涂层的平均摩擦因数为0.208,约是基体(0.442)的1/2;涂层磨损损失量为2.7 mg,约是基体(8.2 mg)的1/3.%Ti/TiBCN composite coating was fabricated on the 7075 aluminum alloy surface by laser cladding technology.The influence of process parameters on the microstructure and properties of the composite coating was studied.The phase composition,microstructure,micro-hardness and wear resistance of the composite coatings were studied by a X-ray diffractometer (XRD),a scanning electron microscope (SEM),a Vickers micro-hardness tester and straight-line-reciprocating dry sliding wear tester,respectively.Results show that the Optimal process parameters are as laser power 1 000 W,scanning speed 3 mm/s and the powder feeding rate 300 mg/min.The top,middle and bottom of the coating are consists of dendrites and cellularn crystals,equiaxed crystal and spherical TiBCN particles,respectively.The average hardness of the coating is 519.4 HV0.2,which is about 4.3 times higher than that of the substrate (～120 HV).The average friction coefficient of the coating is 0.208,which is about half of the substrate (0.442).The mass loss of coating is 2.7 mg,which is about one third of the substrate (8.2 mg).