WC-Co-(Ni)-(Cr)硬质合金在中性溶液中的腐蚀行为

以WC粉、Co粉、Ni粉及Cr3C2粉为原料,采用粉末冶金方法制备了3组不同粘结相成分的WC-Co-(Ni)-(Cr)硬质合金,通过极化曲线测试和浸泡实验研究了3组合金在中性溶液中的腐蚀行为,并采用扫描电镜、能谱分析、X射线光电子能谱(XPS)和EBSD等手段对其腐蚀机理进行了探讨。结果表明,WC-Co和WC-Co-Cr硬质合金在中性溶液中主要发生粘结相Co的腐蚀,浸泡产生的腐蚀产物主要是Co(OH)2;添加Cr将提高WC-Co硬质合金在中性溶液中的耐腐蚀性能,这可能与Cr的添加明显降低了粘结相中密排六方Co的含量有关;同时添加Ni和Cr可进一步提高WC-Co合金在中性溶液中的耐腐蚀性能,在pH=7的Na2SO4溶液中浸泡480 h后,WC-Co-Ni-Cr合金发生很少量的腐蚀。

Corrosion Behavior of WC-Co-(Ni)-(Cr) Cemented Carbide in Neutral Solution

Three groups of WC-Co-(Ni)-(Cr) cemented carbides with different binder phase compositions were prepared by powder metallurgy using WC, Co, Ni and Cr₃C₂ powders as raw materials. The corrosion behavior of the three alloys in neutral solution was studied by polarization curve test and immersion experiment. The corrosion mechanism was discussed by means of scanning electron microscopy, energy spectrum analysis, X-ray photoelectron spectroscopy (XPS) and EBSD. The results show that in neutral solution the corrosion of WC-Co and WC-Co-Cr cemented carbides is mainly caused by the selective dissolution of Co and the corrosion products after immersion are mainly composed of Co(OH)₂. The corrosion resistance of WC-Co cemented carbide in neutral solution can be improved by the addition of Cr, which may be related to the decrease of the content of hcp-Co in the binder phase by adding Cr. Adding Ni and Cr together can further improve the corrosion resistance of WC-Co cemented carbide in neutral solution. After 480 hours immersion in Na₂SO₄ solution, the WC-Co-Ni-Cr alloy sample is just corroded slightly.