Effect of Post-spray Shot Peening Treatment on the Corrosion Behavior of NiCr-Mo Coating by Plasma Spraying of the Shell
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Effect of Post-spray Shot Peening Treatment on the Corrosion Behavior of NiCr-Mo Coating by Plasma Spraying of the Shell–Core–Structured Powders Jia-Jia Tian1 • Ying-Kang Wei1 • Cheng-Xin Li1 • Guan-Jun Yang1 Chang-Jiu Li1
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Submitted: 17 July 2017 / in revised form: 26 October 2017 Ó ASM International 2017
Abstract Corrosion of metal plays a detrimental role in service lifetime of parts or systems. Therefore, coating a protective film which is fully dense and defects free on the base metal is an effective approach to protect the base metal from corrosion. In this study, a dense NiCr-20Mo coating with excellent lamellar interface bonding was deposited by plasma spraying of the novel shell–core– structured Mo-clad-NiCr powders, and then post-spray shot peening treatment by cold spraying of steel shots was applied to the plasma-sprayed NiCr-20Mo coating to obtain a fully dense coating through eliminating possibly existed pores and un-bonded interfaces within the NiCr20Mo coating. Corrosion behaviors of the NiCr-20Mo coatings before and after shot peening were tested to investigate the effect of the post-spray shot peening on the corrosion behavior of the NiCr-20Mo coating. Results showed that a much dense and uniform plasma-sprayed NiCr-20Mo coating with perfect lamellar bonding at most of interfaces was deposited. However, the electrochemical tests revealed the existence of through-thickness pores in the as-plasma-sprayed NiCr-20Mo coating. Through the post-spray shot peening treatment, a completely dense top layer in the coating was formed, and with the increase in
This article is an invited paper selected from presentations at the 2017 International Thermal Spray Conference, held June 7–9, 2017, in Du¨sseldorf, Germany, that has been expanded from the original presentation. & Chang-Jiu Li [email protected] 1
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, Shaanxi Province, People’s Republic of China
the shot peening intensity from one pass to three passes, the dense top layer became thicker from 100 lm to reach 300 lm of the whole coating thickness. Thus, a fully dense bulk-like coating was obtained. Corrosion test results showed that the dense coating layer resulting from densification of shot peening can act as an effective barrier coating to prevent the penetration of the corrosive medium and consequently protect the substrate from corrosion effectively. Therefore, a fully dense bulk-like NiCr-20Mo coating with excellent corrosion resistance can be achieved through the plasma spraying of Mo-clad-NiCr powders followed by appropriate post-spray shot peening treatment. Keywords corrosion interface bonding NiCr coating plasma spraying post-spray shot peening shell–core– structured powder
Introduction Corrosion of metal plays a detrimental role in the lifetime of the engineering part or a system (Ref 1-3). Therefore, a lot of efforts have been made to improve the corrosion resistance o
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