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利用真空原位还原碳化反应合成超细/纳米WC-Co复合粉末,通过添加一定量Cr获得WC-10Co-4Cr复合粉末,经团聚造粒获得喷涂用复合粉末喂料,采用超音速火焰(HVOF)喷涂系统制备出超细/纳米结构的WC-10Co-4Cr涂层。利用X射线衍射仪,扫描电子显微镜和透射电子显微镜对涂层的物相、显微组织结构、元素分布特征等进行了系统表征,并对涂层耐磨性、耐蚀性进行了测试分析。结果表明:基于原位反应合成WC-Co复合粉制备的超细/纳米结构WC-10Co-4Cr涂层具有较好的耐磨性和耐腐蚀性。涂层以WC为主相,含有非晶结构的粘结相Co(Cr),同时存在少量六方晶体结构的W_2C相和非晶复相W_2C+Co(Cr)。对涂层中元素Co和Cr的分布进行了量化分析,得到其从WC晶粒到相界到共晶区再到Co区的变化规律。结合WC-10Co-4Cr复合粉末和超音速火焰喷涂工艺的特点,阐释了Cr在WC-10Co-4Cr涂层分布状态的形成原因,并讨论了对涂层性能的影响。
The WC-10Co-4Cr composite powder was obtained by adding a certain amount of Cr and the composite powder was sprayed by agglomeration and granulation to obtain the ultrafine / nano-WC-Co composite powder. The HVOF ) Spray System Prepared ultrafine / nano-structured WC-10Co-4Cr coating. The phase, microstructure and elemental distribution of the coating were systematically characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The wear resistance and corrosion resistance of the coating were tested. The results show that WC-10Co-4Cr coating prepared by in-situ reaction of WC-Co composite powder has good wear resistance and corrosion resistance. The coating mainly consists of WC, which contains the amorphous phase Co (Cr), while there is a small amount of W_2C phase and amorphous phase W_2C + Co (Cr) with hexagonal crystal structure. The distribution of elemental Co and Cr in the coating was quantitatively analyzed, and the variation of the distribution from WC grains to the eutectic zone to the Co zone was obtained. Combined with the characteristics of WC-10Co-4Cr composite powder and supersonic flame spraying process, the reasons for the formation of Cr-WC-10Co-4Cr coatings were explained, and the influence on the coating properties was discussed.