碳化钨涂层模拟氧化及其对老化性能的影响
Study on Simulated Oxidation of WC Coating and its Effect on Aging Performance
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摘要: 为了分析国产某大型装备关键部件表面喷涂的钴-碳化钨涂层在厂房放置后出现蓝紫色现象,并评估其对涂层服役性能的影响,采用同样的超音速火焰喷涂工艺制备一批钴-碳化钨涂层样品,利用环境试验箱调节湿度和温度,模拟现场环境进行加速氧化试验并实时观察。采用拉拔法、往复摩擦法和电化学试验对腐蚀后的样品进行结合力、摩擦以及抗腐蚀性能测试。发现采用同样参数制备的钴-碳化钨涂层在模拟条件下成功复现了现场腐蚀样貌。对比研究腐蚀前后钴-碳化钨涂层各项性能发现,腐蚀前后涂层的结合力均大于60 MPa;腐蚀前后涂层同条件下的磨损体积基本一致,无明显下降;腐蚀氧化仅发生在涂层表面,未深入涂层内部,涂层内部和基体并无损伤。分析认为,现场发生的涂层表面变色是由于当地夏季环境高温高湿,导致涂层表面发生Co的氧化。氧化后涂层的结合强度和耐磨性无明显下降,经过综合研究认定,现场涂层表面氧化不会影响其服役性能及寿命。Abstract: The WC-17Co coating sprayed on the surface of key parts of a set of large domestic equipment becomes blue and purple locally when placed in the plant for a period of time. To study the reason for that and evaluate its impact on the coating service performance, a batch of WC-17Co coating samples are prepared. An environmental test box is used to adjust humidity and temperature to simulate the field environment for accelerated oxidation tests and in-situ observation. The adhesion, wear-resistance, and corrosion resistance are tested by pull-out method, reciprocating friction method, and electrochemical measurements. It is found that the WC-17Co coating prepared with the same parameters successfully reproduced the field corrosion appearance under the simulated conditions. By comparing the properties of WC-17Co coating before and after the corrosion, it is found that the adhesion strengths of the coating before and after the corrosion are higher than 60 MPa. The wear volume of the coating before and after the corrosion changes little. The corrosion only occurs on the surface of the coating, and the interior of the coating and substrate are not damaged. It can be concluded that the surface discoloration of the coating is due to the high temperature and humidity of the local summer environment, resulting in Co oxidation of the coating surface. The adhesion and wear-resistance of the oxidized coating are not significantly reduced. Therefore, the surface oxidation of the field coating will not affect its service performance.