U71Mn钢激光熔覆钴基熔覆层耐磨性研究

Study on Wear Resistance of Laser Cladding Cobalt Based Cladding Layer of U71Mn Steel

为提高U71Mn钢的耐磨性,延长钢轨的使用寿命,选择Stellite6粉、TiC粉和Y_(2)O_(3)粉为熔覆粉末,采用激光熔覆同轴送粉技术在U71Mn钢基体表面制备钴基合金熔覆层。利用光学显微镜、扫描电子显微镜、X射线衍射仪、显微硬度仪器、超景深显微镜、磨损试验机,分析熔覆层宏观形貌、显微组织、物相组成、显微硬度、磨损形貌和摩擦磨损性能。研究表明,在质量分数为10%TiC-钴基粉末中添加粉末总质量2%的Y_(2)O_(3)粉末,可获得较好的单道熔覆层;在激光功率为1200 W,扫描速度为5 mm/s,送粉速度为1.0 r/min,搭接率为40%时,可获得表面最为平整的熔覆层。熔覆层显微组织由等轴晶和柱状晶组成,熔覆层与基体冶金结合良好,熔覆层主要由TiC、Cr_(7)C_(3)、Cr_(23)C_(6)、γ-Co和Co_(3)Ti组成。熔覆层硬度最高可达572 HV,平均硬度约为基体的1.8倍;熔覆层磨损量为基材磨损量的3.83%,钴基熔覆层的耐磨损性能显著提升。

In order to improve the wear resistance of U71Mn steel and prolong the service life of rail,Stellite6 powder,TiC powder and Y_(2)O_(3)powder were selected as cladding powder,and cobalt alloy cladding layer was prepared on the surface of U71Mn steel by laser cladding coaxial powder feeding technology.optical microscope,scanning electron microscope,X-ray diffractometer,microhardness instrument,ultra depth of field microscope and wear testing machine were used to analyze the macroscopic morphology,microstructure,phase composition,microhardness,wear morphology and friction and wear properties of the coating,respectively.Results show that the best single channel cladding layer can be obtained by adding 2%Y_(2)O_(3)powder to 10%TiC-Cobalt-based powder.When the laser power is 1200 W,the scanning speed is 5 mm/s,the powder feeding speed is 1.0 r/min and the lap rate is 40%,the most flat cladding layer can be obtained.The microstructure of the cladding layer is composed of equiaxed and columnar crystals.The cladding layer has good metallurgical bonding with the matrix.The cladding layer is mainly composed of TiC,Cr_(7)C_(3),Cr_(23)C_(6),γ-Co and Co_(3)Ti.The hardness of the cladding layer is up to 572 HV,and the average hardness is about 1.8 times that of the matrix.The wear of the cladding layer is 3.83%of the wear of the substrate,and the wear resistance of the cobalt-based cladding layer is significantly improved.