原位回火对马氏体不锈钢激光熔覆涂层的影响

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

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。

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.