超音速激光沉积法制备Ni60涂层的显微组织及沉积机理

Microstructure and Deposition Mechanism of Ni60 Coatings Prepared by Supersonic Laser Deposition

超音速激光沉积技术（SLD）是一种将激光辐照与冷喷涂相结合的新型涂层制备工艺,因其结合了激光技术和冷喷涂技术的优势,能够沉积冷喷涂难以沉积或不可能沉积的材料。利用超音速激光沉积技术在中碳钢基材上成功制备了Ni60涂层,并采用扫描电子显微镜（SEM）、能谱分析（EDS）、X射线衍射（XRD）、显微硬度测试等手段对涂层的沉积效率、显微组织成分、结合机理以及显微硬度进行了表征分析。研究结果表明：随着激光加热温度升高,涂层沉积厚度增加,表面球型凹坑逐渐减少;Ni60涂层保持了冷喷涂固态沉积的特征,显微组织结构以及相组成与原始粉末相一致;激光加热导致Ni60沉积层与基体间同时存在机械咬合与冶金结合;涂层的平均显微硬度为867 Hv0.3,比原始粉末提高8%~10%,沉积过程产生了冷作硬化。

As a new composite spraying technology combining the advantages of laser and cold spray, supersonic laser deposition（SLD） is able to deposit materials which are difficult or impossible to deposit by cold spray technique alone. Ni60 coatings are successfully fabricated on the surface of medium carbon steel by SLD. The deposition efficiency, bonding mechanism, microstructure, composition and micro-hardness are characterized by scanning electron microscope（SEM）, energy dispersive spectrometer（EDS）, X-ray diffraction（XRD） and microhardness tester, respectively. The results show that the thickness of deposited layer significantly increases with the rising of deposition temperature, the spherical indentation on surface decreases. Compared with Ni60 particles,the Ni60 deposited coating preserves the status of solid-state deposition, and has the same microstructure and phase with powder. The bonding mechanism is mainly mechanical interlocking and metallurgical bonding under laser irradiation. Average micro-hardness of the deposited coating is 867 Hv0.3, which is 8%~10% higher than that of the original powder due to cold hardening.