抑制剂对WC-Co硬质合金涂层性能的影响

利用原位还原碳化反应合成的超细WC-12Co复合粉末作为原料, 分别添加1.0wt%晶粒长大抑制剂即VC、Cr₃C₂和NbC, 经团聚造粒和超音速火焰(HVOF)喷涂制备了超细结构的硬质合金涂层。研究了不同晶粒长大抑制剂对涂层的显微组织结构、物相、硬度、耐磨性能和耐蚀性能的影响。结果表明, 与未添加晶粒长大抑制剂涂层相比, 添加1.0wt% VC或Cr₃C₂制备的硬质合金涂层中WC颗粒的平均尺寸降低了约49%, 涂层硬度明显提高, 磨损速率降低了约52%~55%。添加1.0wt% NbC对制备涂层中WC颗粒尺寸的抑制作用不明显, Co粘结相中由于形成了(W, Nb)C化合物, 其耐蚀性获得显著提高, 但该化合物脆性大, 导致涂层耐磨性不及添加VC和Cr₃C₂制备的涂层。

Grain Growth Inhibitor on the WC-Co Cemented Carbide Coating

The ultrafine WC-12Co composite powder was synthesized by in situ reduction and carbonization reactions. Using the composite powder with an addition of 1.0wt% grain growth inhibitor (GGI) i.e. VC, Cr₃C₂ and NbC, as raw materials, the ultrafine-structured cemented carbide coatings were fabricated by the high velocity oxy-fuel (HVOF) spraying method. Prior to thermal spraying, the powders were agglomerated into thermal spray feedstock. The effects of GGI addition on phase constitution, microstructure, hardness, and wear and corrosion properties of the coatings were investigated. The results show that the mean WC particle size of coatings with an addition of 1.0wt% VC or Cr₃C₂ decreases by about 49% as compared to that without GGI. Moreover, hardness of the coatings is significantly improved and the wear rate decreases by 52%-55%. Addition of 1.0wt% NbC has little effect on WC particle size of the coating but leads to formation of (W, Nb)C compound in the Co binder. Thus the corrosion resistance of the coating containing NbC is significantly enhanced. However, its wear resistance is lower than those with VC or Cr₃C₂, due to high brittleness of the (W, Nb)C compound.