等离子喷涂WC-Co涂层的微观组织及硬度

Microstructure and Hardness Properties of Low Power Plasma Sprayed WC-Co Cermet Coatings

以普通低碳钢Q235A为基体,钴基碳化钨陶瓷粉末WC-12Co为热喷涂材料,采用低功率(5.2 kW～9.1 kw)内送粉等离子喷涂方法,在保持等离子弧电流恒定的情况下,通过改变弧电压来制备不同功率下的WC-Co陶瓷涂层。利用扫描电子显微镜(SEM)和X射线衍射仪对涂层的显微组织和相结构进行观察与分析,并使用MH-6维氏硬度仪测量涂层的显微硬度HV,研究喷涂条件对形成的WC-Co陶瓷涂层微观组织、相组成和硬度的影响规律。结果表明:原始喷涂粉末的XRD图谱中仅能观察到主相WC和极少量的金属Co,而低功率等离子喷涂WC-Co陶瓷涂层中则除了WC相以外,还含有W_2C,Co_3W_3C,Co_3W_9C_4等其它相,并且随着等离子喷涂功率的增加,WC衍射峰强度降低,而包括W_2C在内的其它相衍射峰强度升高。等离子喷涂WC-Co涂层微观组织为大量硬质相(WC,W_2C,Co_3W_3C或Co_3W_9C_4)颗粒弥散分布于较软的富Co粘结剂之中。保持等离子弧电流130A不变,涂层显微硬度随弧电压升高呈现先下降后上升的变化规律,并且电压70 V时涂层具有最高的显微硬度。

Thermal spray cermet powders WC-12Co were sprayed onto mild steel Q235A substrate by low power plasma spraying （5.2 kW-9.1 kW） with internal particle injection. The WC-Co cermet coatings were prepared at different plasma power by keeping the arc current constant and changing the arc voltage. The as-sprayed coatings were examined by XRD and SEM to evaluate the phase composition and microstrueture. The microhardness tests were performed using MH-6 micro-hardness tester. The influence of plasma spray parameters on the coatings microstructure, phase composition and hardness had been investigated. The XRD patterns indicated that, the starting powders consisted of a dominant WC and a minor Co, but the phase assemblage of as-sprayed coatings included not only WC but also W2C, Co3W3C and Co3W9C4. Moreover, WC peak intensity decreased while that of other phases besides W2C increased as the plasma power increased. And it was found that hard particles such as WC, W2C, Co3W3C and Co3W9C4 were dispersedly distributed in soft Co matrix, and the hardness of the coatings mainly depended on the Co binder thickness and the way that hard particles were distributed. As plasma power increased, the hardness of the coatings decreased initially but later increased and at high arc voltage of 70 V, the hardness was the highest.