等离子喷涂镍基可磨耗封严涂层抗腐蚀及耐磨性能分析

Corrosion Resistance and Anti-wear Property of Nickel Based Abradable Sealing Coating Deposited by Plasma Spraying

采用高效能超音速等离子喷涂沉积Ni-C及Ni Cr Al-BN可磨耗封严涂层,对比研究两种涂层的抗冲蚀磨损、耐腐蚀及摩擦磨损性能。结果表明:两种涂层中的润滑相均匀分布在金属连续相之中,但与Ni-C涂层相比,Ni Cr Al-BN涂层中的润滑相尺寸较为细小,表面硬度较高。当冲蚀角度由30°增加到90°后,两种涂层冲蚀磨损失重量明显提高。Ni Cr Al-BN涂层的相对冲蚀速率约为Ni-C涂层的50%,表明Ni Cr Al-BN涂层具有较为优良的抗冲蚀性能。Ni-C涂层在稀盐酸中(1vol%)发生了明显的电化学腐蚀,在石墨片周围容易形成腐蚀产物;酸液会沿Ni Cr Al-BN涂层中的孔隙渗入,从而造成金属的局部腐蚀,但腐蚀程度明显较Ni-C轻。随着环境温度的升高,以BN为主的第二相润滑组元的塑性和流动性增强,使摩擦表面原本较小的、不连续的润滑型保护膜逐渐铺展开来,形成面积较大且呈连续分布的鳞片状自润滑保护膜。原来在较低温度下润滑膜中存在的裂纹、疏松或剥离等缺陷明显减少,导致Ni Cr Al-BN涂层摩擦系数大幅度降低,从而显示出优异的高温自润滑性能。

High-efficiency supersonic atmospheric plasma spraying was used to fabricate Ni-C and NiCrA1-BN abradable seal coatings. The erosion wear, corrosion resistance and wear resistance of plasma-sprayed coatings were comparatively studied. Experimental results showed that the libricating phases were homogeneously distributed in the as-sprayed coatings while their average size of the coating was much fine compared with Ni-C coating, and the former also showed higher surface hardness than the latter. Meanwhile, it was found that the erosive mass loss increased with the increase of impingement angle from 30° to 90° and the relative erosion rate of NiCrA1-BN coating was only a half of that of Ni-C coating. Due to the formation of corrosion product around the flake graphite, the corrosion resistance of NiCrAl-BN coating was better than Ni-C coating in dilute hydrochloric acid （lvol%）. However, the hydrochloric acid could permeate the NiCrAl-BN coating through the pores, which resulted in the localized corrosion of metal phases. In addition, we also observed that the friction coefficient of NiCrAl-BN coating significantly decreased from room temperature to 400 ℃ owing to the formation of large-scale self-lubricating film that resulted from the improvement of plasticity and fluidity of BN.