连接层和退火对HVAF喷涂Cr_3C_2-NiCr涂层性能的影响

Effect of Bond Coat and Annealing on the Properties of HVAF Sprayed Cr_3C_2-NiCr Coating

本文使用HVOF和HVAF技术在铜合金上喷涂Cr_3C_2-50wt%Ni Cr涂层,并就NiCr连接层和退火对HVAF喷涂层的耐磨性和耐腐蚀性进行研究。通过对涂层物相组成、显微结构、力学性能、摩擦磨损性能以及电化学动力学曲线进行测试。结果发现:HVAF喷涂层具有比HVOF更高的结合强度,且磨损体积差异较小,但致密的HVOF喷涂层其耐腐蚀性能优于HVAF喷涂层;NiCr连接层的添加提高了复合涂层的结合强度,且致密的连接层结构可阻碍腐蚀液向基体的侵蚀,使复合涂层的耐腐蚀性能提升;退火处理通过消除涂层内部缺陷提高组织致密性,使得耐腐蚀性增强,并且退火处理降低了涂层内部残余应力,导致涂层结合强度和耐磨性能提升;300℃磨损条件下,喷涂层的磨损机制包括黏着磨损、磨粒磨损和局部氧化磨损。

Cr3C2-50wt%NiCr coatings were sprayed on CrZrCu alloy by HVOF and HVAF technique in this paper. The effects of NiCr bond coat and annealing treatment on HVAF sprayed Cr3C2-50wt%NiCr coating were studied also. The phase composition, micro- structure, mechanical property, wear property and potential d5〇 iamic polarization of sprayed coatings were investigated in detail. The results showed that HVAF sprayed coating possesed higher adhesion strength and the similar wear loss with HVOF sprayed coating. But the HVOF sprayed coating showed dense structure and performed better corrosion resistance. The addition of NiCr bond coat increased the adhesion strength of the composite coatings. Moreover, the dense structure of bond coat can prevent the damage of corrosion ions from stopping the propagating path to substrate, which result in better corrosion resistance. Annealing treatment increased the corrosion resistance of HVAF sprayed bi-layers by releasing thedefect inside coating, and it decreased the residual stress so as to increasing the adhesion strength and wear resistance. The wear mechanisms of sprayed coatings under 300 ℃ surroudings concludes abrasive wear, adhesive wear and localized oxidative wear.