【作者】 陈鹏荣；

【导师】 孔凡涛；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2010， 硕士

【摘要】 钴基自熔性合金粉末是一种优良的耐热、耐蚀、耐磨、抗高温氧化的材料,广泛应用于制备耐磨涂层。等离子喷涂技术由于操作工艺简单、喷涂效率高、涂层厚度可控等优点被广泛应用于制备涂层。为改善12Cr1MoV钢的表面性能、降低成本,本文采用等离子喷涂技术制备出钴基涂层以及不同WC含量的钴基复合涂层,并对涂层进行重熔处理,分析了重熔前后涂层的组织与性能。钴基自熔性合金粉末经10h球磨后发现,粉末仍由γ-Co-固溶体基体和Cr23C6相组成,但颗粒尺寸得到显著细化,平均粒度从约200μm降低到70μm左右。将球磨后的钴基粉末,在不同喷涂电流条件下进行等离子喷涂,发现在喷涂电流为500A时,钴基涂层的孔隙率最低,相组成没有发生变化,涂层与基体之间为机械结合。性能测试的研究结果表明,喷涂电流为500A时,钴基涂层硬度值较高为447.8 HV;涂层摩擦系数较低,保持在0.42左右,磨损表面磨痕较浅;涂层的自腐蚀电位为-583mv,自腐蚀电流密度较小。综合分析表明钴基涂层在喷涂电流500A时涂层的性能较优。通过在钴基粉末中添加不同含量的WC颗粒（WC含量:10wt%、15wt%、20wt%）发现,在500A条件下喷涂后,部分WC在高温下发生分解生成W2C,涂层孔隙率有所增加,且随着WC添加量的增多,孔隙率是逐渐增高。界面分析发现,复合涂层与基体间为机械结合。显微硬度测试及摩擦磨损实验研究结果表明,含20wt%WC的复合涂层硬度值达715.2HV,但摩擦系数不稳定。当添加15%WC时,涂层硬度值为664.5HV,摩擦系数稳定约为0.40。通过耐蚀性研究发现当WC添加量为15%时,自腐蚀电位为-576mv,一次钝化区间（约155mv）,自腐蚀电流密度较低（1.57×10-8A/cm²）。综合分析,WC添加量为15%时,复合涂层性能较优。对钴基涂层（喷涂电流为500A）及复合涂层（ WC含量15wt%）进行1050-1150℃下重熔发现,涂层界面处元素发生扩散,钴基涂层中有Co₃B及Co₆W₆C相生成,复合涂层中形成Co₂C及Co₆W₆C。随着重熔温度的升高,涂层孔隙率明显减少,涂层组织更加均匀,元素扩散越明显。在重熔温度达到1150℃时,涂层层状结构消失,颗粒间产生熔合,涂层的界面结合强度得到明显改善。性能测试研究结果表明,重熔后涂层硬度有所降低。钴基涂层经1100℃处理后,硬度最高（422HV）,但摩擦系数在稳定一段时间后上升;自腐蚀电位为-480mv,一次钝化区间增至455mv。复合涂层经1150℃处理后,硬度最高（621HV）,摩擦系数稳定保持在0.33左右;复合涂层的自腐蚀电位为-553mv,变化不大,但一次钝化区间增大到500mv,维钝电流较低。更多还原

【Abstract】 The powder of cobalt-based self-fluxing alloy has been widely used in wear-resistant coating because of the excellent performance such as heat resistance, corrosion resistance, wear resistance, high temperature oxidation resistance and so on. Plasma spraying has been widely used to make coating because operation is simple, efficiency of spraying is high and the thickness of the coating is controllable. In this article the Co-base coating and Co-base compound coating containing different proportions of WC were prepared by using plasma spraying in order to improve surface properties of 12Cr1MoV and reduce cost. Then remelting treatment was adopted. The organization and properties were investigated before and after remelting treatment.The powder of cobalt-based self-fluxing alloy was refined by Mixing Mill for 10h. The phases were stillγ-Co and Cr₂₃C₆.However, the size of powder was significantly refined from 200μm to 70μm. The Co-base coating was prepared at different spraying currents. It was discovered that the value of porosity was the minimum and phases did not change at 500A. The combination between coating and substrate was mechanical. Results of the measurement revealed that the hardness value of Co-base coating was 447.8HV and the friction coefficient was stably kept at 0.42. The wear scars were shallow on the surface. The corrosion potential of Co-base coating was -583mv. The corrosion current density was lower when spraying current was 500A. The Co-base coating has better performance when the spraying current was 500A.Different proportions of WC （10wt%、15wt%、20wt%） were added in Co-base alloy powder. The organization of compound coating at 500A was investigated. It was found that the porosity increased with the proportions of WC rising and WC has been decomposed to W2C at high temperature. By interface analysis, the combination between coating and substrate was mechanical. Study on microhardness and wear resistance of the coating, the hardness value of 20%WC compound was 715.2HV, however the friction coefficient was unstable. The hardness value of 15%WC compound coating was 664.5HV and the friction coefficient was about 0.40. After corrosion resistance testing, the corrosion potential of 15%WC compound coating was found to be -576mv, passivation current density was lower （1.57×10-8A/cm2）. The 15%WC compound coating has better performance than others.Some elements were diffused between interface of coating and substrate after remelting treatment at 1050-1150℃. Co₃B and Co6_W6C were added into Co-base coating and Co₂C and Co₆W₆C were added into compound coating after remelting treatment. With the increase of temperature, the porosity significantly reduced, the organization was becoming uniform and element diffusion was much more obvious than before. The layer structure of the coating disappear, particles have been fusion and bonding strength of coating noticeably improved at 1150℃. The hardness of Co-base coating and compound coating were slightly decreased after remelting treatment. The highest hardness value of Co-base coating appeared at 1100℃, but the coefficient friction was increased after few minutes. The corrosion potential of Co-base coating was -480mv and the region of passivation reached about 455mv at 1100℃. The compound coating has the highest hardness （621HV） at 1150℃and coefficient friction was stable at 0.33. The corrosion potential of compound coating did not change a lot, but the region of passivation reached about 500mv at 1150℃.更多还原