原位回火对马氏体不锈钢激光熔覆涂层的影响

目的 提高马氏体不锈钢(MSS)激光熔覆涂层的综合性能。方法 利用光纤激光器在Q235钢基材表面，分别采用连续扫描、间断扫描(层间停留30 s)两种方式，制备420 MSS激光熔覆涂层。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、万能材料试验机、维氏显微硬度计、电化学工作站等设备，对比表征了不同扫描方式下制备的涂层试样的显微组织、力学性能和耐蚀性能。结果 连续扫描试样的显微组织分布均匀，主要由马氏体(M)和少量残余奥氏体(Ar)组成，呈脆性断裂，其抗拉强度和断后延伸率分别为1368 MPa、3.91%。而间断扫描试样由于产生了原位回火效应，存在两类不同组织:一类是细小灰色组织，比例分数为89.8%，由回火马氏体(Mtmp)、弥散分布的D23C6颗粒(D为Fe、Cr等)和少量Ar组成;另一类是粗大亮白色组织，比例分数为10.2%，主要为未回火M(un-tempered M)。间断扫描试样的抗拉强度和断后延伸率分别为1694 MPa、12.46%，但显微硬度和耐蚀性略有下降。结论 原位回火处理可显著提高420 MSS激光熔覆涂层的强韧性。

Effects of In-situ Tempering on the Laser-cladded Martensitic Stainless Steel Coating

The work aims to improve the comprehensive properties of the laser-cladded martensite stainless steel (MSS) coating. Fiber laser was utilized to prepare 420 MSS coatings on Q235 steel substrate by continuous scanning and idle scanning (the laser was switched off 30 s between layers), respectively. The microstructure, mechanical properties and corrosion resistance of the coating specimens prepared by different laser scanning modes were characterized by equipment such as X-ray diffractometer (XRD), scanning electron microscope (SEM), universal material testing machine, Vickers microhardness tester and electrochemical workstation. The microstructure of the continuous scanning specimen was uniformly distributed, mainly composed of martensite (M) and a small amount of residual austenite (Ar), exhibiting brittle fracture with the tensile strength of 1368 MPa and elongation of 3.91%. The idle scanning specimen consisted of two different types of microstructure due to the in-situ tempering effect. One was the fine gray microstructure, accounting for 89.8%, which was composed of tempered martensite (Mtmp), dispersed-distributed D23C6 particles (D was Fe, Cr, etc.) and a small amount of Ar. The other was coarse bright white microstructure, accounting for 10.2%, which was mainly composed of un-tempered M. The idle scanning specimen exhibited the tensile strength of 1694 MPa and elongation of 12.46%, but the microhardness and corrosion resistance slightly decreased. The strength and ductility of the laser-cladded 420 MSS coating can be significantly improved by in-situ tempering effect.