激光熔覆TiC颗粒增强Fe基梯度涂层的耐磨性能

Wear Resistance of Laser Cladding TiC Particle-Reinforced Fe-based Gradient Coating

摘要:

采用激光熔覆的方法将TiC颗粒增强铁基粉末熔覆在40Cr钢基体上制备高硬度耐磨梯度陶瓷涂层。利用扫描电镜（SEM）、能谱仪（EDS）、X射线衍射仪（XRD）、显微硬度计、摩擦磨损试验机对熔覆层的微观组织、物相、硬度及耐磨性进行研究。结果表明：熔覆层物相主要为奥氏体相、TiC强化相，并有少量铁素体相，激光熔覆TiC颗粒增强粉末制备的金属陶瓷涂层组织致密、物相与粉末组成基本一致；TiC 强化相在熔池底部到顶部呈梯度分布，熔池中TiC强化相部分溶解、尺寸减小，部分受激光热作用长大呈四方形、雪花状、鱼骨状，TiC相在熔池底部呈现3种生长方式，且TiC增强相分布较少，熔池中部TiC增强相逐渐增多，熔池上部TiC增强相出现富集并桥接生长；熔覆层维氏硬度HV高达19 602.94 MPa，同等条件下，涂层的摩擦磨损深度为基体的1/5，显著提高了基体的耐磨性。

Abstract:

A high-hardness, wear-resistant gradient ceramic coating was prepared by laser cladding TiC particle-reinforced iron-based powder onto a 40Cr steel substrate to achieve the coating's gradient effect. Scanning electron microscope (SEM), energy dispersive spectroscope (EDS), X-ray diffractometer (XRD), micro-hardness tester, and friction and wear tester were used to investigate the microstructure, phase, hardness, and wear resistance of the cladding layer. Results show that the phase of the cladding layer is mostly austenite, some TiC strengthening phase, and a trace amount of ferrite phase. The cermet coating made of laser cladding TiC particle-reinforced powder has a compact microstructure, and the coating phase composition is essentially the same as the powder composition. The TiC phase, which is responsible for the strengthening effect, is dispersed across the molten pool following a gradient from the bottom to the top. The TiC phase reinforcing the molten pool is partly dissolved, and thus the size of the pool shrinks. Under the laser's intense heat, some TiC strengthening phases develop into shapes like squares, snowflakes, and fish bones. At the base of the molten pool, the TiC phase may develop in three ways, while the TiC strengthening phase is less widely dispersed. The TiC strengthening phase in the center of the molten pool is progressively expanded, and enriched and bridged in the top portion of the molten pool. The cladding layer has a Vickers hardness HV up to 19 602.94 MPa, and under the same circumstances, the friction and wear depth of the coating is only one-fifth of that of the substrate. This results in a considerable improvement in the wear resistance of the substrate.