采用光纤激光在不锈钢上制备得到了Stellite 6涂层。观察不同温度热处理对显微组织的影响。以氧化铝作为对磨件,在销盘式高温摩擦试验机上研究了涂层在不同温度下(600,700,800,900 ℃)的摩擦磨损行为,以确定涂层适用的工作温度区间。结果显示涂层物相主要为fcc和hcp型富Co固溶体以及碳化物共晶组织,700 ℃时涂层显微组织稳定,800 ℃和900 ℃热处理后涂层共晶组织分解严重,并伴有细小颗粒二次析出,富Co固溶体在700~800 ℃之间从fcc型转变为hcp型。Stellite 6高温摩擦时,磨损主要发生在摩擦初期,一旦釉质层形成,磨损量大幅下降,在700 ℃下涂层磨损量最小。600 ℃时的高温摩擦机制是犁削磨损和黏着磨损,涂层表面能形成少量与涂层结合不紧密的釉质层;700 ℃和800 ℃时转为磨粒磨损和黏着磨损,釉质层致密;900 ℃时涂层因过度软化而在摩擦初期就发生严重的塑性变形。可以推断Stellite 6的合适工作温度在700~800 ℃之间。

Stellite 6 coating is cladded on the stainless steel using a fiber laser. The effect of heat treatment on the microstructure of the coating is investigated at various temperatures. Further, a tribometer with a pin-on-disk configuration at high temperatures (600 ℃, 700 ℃, 800 ℃, and 900 ℃) is used to evaluate the sliding wear behavior of the coating during interaction with alumina for identifying the applicable working temperature range of the coating. The results denote that the coating predominantly comprises carbide eutectics and a Co-rich solid solution exhibiting fcc and hcp structures. The microstructure of the coating is thermally stable at 700 ℃. However, the eutectics are critically decomposed with the secondary precipitation of fine particles after heat treatments at 800 ℃ and 900 ℃. The transformation temperature from fcc to hcp structures of Co-rich solid solution is 700-800 ℃. In case of the Stellite 6 coating, wear at high temperature can be observed during the initial stage of the friction process. The wear loss drastically decreases once the glaze layer is formed. Among the friction temperatures, the wear loss at 700 ℃ is observed to be the lowest. Ploughing and adhesion are the wear mechanisms at 600 ℃. Slight glaze layer is formed on the surface of the coating, which is loosely bound with the coating. At 700 ℃ and 800 ℃, the coating exhibits abrasion and adhesion, and compact glaze layer is formed and bound tightly with the coating. At 900 ℃, the coating is considerably softened, leading to tough plastic deformation during the initial stage of the friction process. Therefore, the applicable working temperature range of the laser-cladding Stellite 6 coating is 700-800 ℃.