汽轮机末级叶片用SP-700钛合金激光熔覆Zr涂层工艺参数优化

Process Parameter Optimization of Zr Coating on SP-700 Titanium Alloy by Laser Cladding on the Last Stage Blade of Steam Turbine

采用激光熔覆技术在SP-700钛合金表面制备Zr涂层,研究了扫描速度和送粉器转速对激光熔覆层的形貌影响,以获得最佳工艺。通过光学显微镜表征其搭接宽度、熔厚和裂纹率等特征参数;通过扫描电镜(SEM)分析了不同激光熔覆工艺下渗层组织结构、熔厚及其与基体的结合界面等;利用显微维氏硬度仪、往复式摩擦磨损实验机和激光共聚焦显微镜测试了熔覆层的显微硬度、磨擦因数、磨损形貌和耐磨性等。结果表明:扫描速度为6 mm/s、送粉器转速为4 r/min时,表面成型质量较优,熔厚和搭接宽度处于中等,熔覆层的裂纹率较低;熔层内组织分布均匀,晶体清晰,弥散度低;显微硬度较高,整体相对基体提升了1.8倍;摩擦磨损形貌较好,无明显缺陷,耐磨性较佳。

Zr coating layer was prepared on SP-700 titanium alloy by laser cladding.The effect of scanning speed and powder feeding rate on the coating morphology was studied to obtain the best process.The characteristic parameters such as lap width,melting thickness and crack rate were obtained by optical microscopy.The structure,melting thickness and interface of the under layer at different scanning speed and powder feeding rates were characterized by scanning electron microscopy(SEM).The microhardness,friction coefficient,wear morphology and wear resistance of the cladding layer were determined by vickers microhardness meter,reciprocating friction tester and laser confocal microscopy.Results show that at the scanning speed of 6 mm/s and the rotation rate of powder feeder of 4 r/min,better surface forming quality,medium melting thickness and lap width,lower crack rate of the cladding layer,uniform microstructure,clear crystal,low dispersion and higher microhardness can be achieved.The microhardness of coating layer is 1.8 times higher than the matrix.The morphology of friction and wear is good.No obvious defects are detected.The wear resistance is better.