超音速火焰喷涂86WC-10Co-4Cr涂层的抗氧化性能

On the Anti-oxidation Property of 86WC-10Co-4Cr Coating by High Velocity Oxy-fuel Spraying

86WC-10Co-4Cr是WC基金属陶瓷涂层中最具代表性的一种涂层材料,WC基涂层材料的失效与其工作温度密切相关,研究86WC-10Co-4Cr涂层在空气中的氧化行为并得出其适宜的工作温度具有重要的意义。试验利用超音速火焰喷涂设备制备高致密度的86WC-10Co-4Cr涂层,利用X射线衍射、扫描电镜、显微硬度计等分析检测手段对涂层氧化前后物相、微观形貌及显微硬度进行表征,并对涂层材料的氧化机制和显微硬度下降原因进行了探讨。结果表明:粉末喷涂过程中会造成少量WC相脱碳和金属相非晶化;86WC-10Co-4Cr涂层在500℃以下具有优良的抗氧化性能,在500℃以上涂层氧化后孔洞增多且出现微裂纹,高温下涂层中的WC、W2C以及金属相Co与Cr与空气中的O2发生反应生成WO3、CoWO4和CrWO4;氧化后涂层的显微硬度随氧化温度升高而降低,涂层在540℃的显微硬度仅为566.76,与氧化前相比下降了54.07%,氧化物生成及孔洞和微裂纹的出现是导致涂层显微硬度明显下降的主要原因。

86 WC-10 Co-4 Cr is the most representative coating material in WC-based cermet coating. The failure of WC-based coating material is closely related to its working temperature. It is of great significance to study the oxidation behavior of 86 WC-10 Co-4 Cr coating in air and to obtain its suitable working temperature. A high density86 WC-10 Co-4 Cr coating was prepared by high velocity oxy-fuel in this article. The phase, microstructure and micro-hardness of the coatings before and after oxidation were characterized by X-ray diffraction, scanning electron microscopy and micro-hardness tester respectively. The oxidation mechanism of coating materials and the reasons for the decrease of microhardness were discussed. The results showed that a small amount of WC phase decarburization and metal phase amorphization was caused during powder spraying. The 86 WC-10 Co-4 Cr coating had excellent oxidation resistance under 500 ℃. After oxidation of the coating above 500 ℃, the pores increased and microcracks appeared. The WC, W2 C, Co and Cr in the coating reacted with the O2 in the air to form WO3, CoWO4 and CrWO4 under high temperature. The microhardness of the coating decreased with the increase of oxidation temperature. The microhardness of the coating at 540 ℃ was only 566.76, which was 54.07 % lower than that before oxidation. The formation of oxide and the appearance of pores and microcracks were the main reasons for the apparent decrease of the microhardness of the coating.