Effect of Substrate Surface Texture Shapes on the Adhesion of Plasma-Sprayed Ni-Based Coatings
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Effect of Substrate Surface Texture Shapes on the Adhesion of Plasma-Sprayed Ni-Based Coatings Xianghua Zhan1 • Yancong Liu1,2 • Peng Yi1 • Wenlong Feng1 • Zhihao Feng1 Yanchao Jin1
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Submitted: 9 August 2020 / in revised form: 5 November 2020 / Accepted: 9 November 2020 Ó ASM International 2020
Abstract The bonding of thermal-sprayed coatings largely depends on the substrate surface morphology. This study examines the effect of the substrate surface texture shapes on the adhesion strength of coatings. For that, it used plasma-sprayed Ni-based MoS2 coatings deposited on gritblasted and laser-textured surfaces, and investigated the coating bonding strength (ASTM 633 pull-off test), and cross-sectional and fracture morphologies, as well as phase compositions and element distribution. The results showed that the surface texture shape has a significant effect on the improvement of coating adhesion. The coatings deposited on sinusoidal-textured surfaces had the highest adhesion strength (50.0 MPa), followed by coatings deposited on groove-textured surfaces, while dimple and dimple–groove textures resulted in the lowest coating adhesion strength. The coating fracture analysis revealed that cohesive failure occurred mainly at the texture positions, while adhesive failure occurred almost always in plain areas. Therefore, it could be concluded that, in the conditions of this study, the existence of plain areas and dimple textures did not improve coating adhesion. Factors such as coating bond mode, contact area ratio, and coating deposition quality should be comprehensively considered in texture design to improve coating adhesion.
& Peng Yi [email protected] 1
College of Mechanical and Electronic Engineering, China University of Petroleum, No. 66 Changjiang West Road, Huangdao District, Qingdao 266580, China
2
School of Mechanical and Control Engineering, Shengli College of China University of Petroleum, Dongying 257061, Shandong, China
Keywords atmospheric plasma spray coating adhesion laser texturing pull-off test texture shape
Introduction The good adhesion of solid lubricants to substrate surfaces is necessary to ensure the presence of these lubricants on friction pair surfaces even at high shear stresses (Ref 1). Solid lubricant coatings have attracted increasing attention in recent years due to their excellent film-to-substrate bonding performance and extremely low friction and wear coefficients under certain or highly controlled test conditions (Ref 2). Numerous methods, including powder metallurgy, vapor deposition, thermal spray, and cold spray, have been developed for the fabrication of strongly bonded coatings on various substrates (Ref 3-6). Plasma spraying is one of the most commonly used techniques (Ref 7). The bond strength of coatings strongly depends on substrate topography, coating temperature gradient, residual stresses, and surface composition (Ref 8-10). Grit blasting (GB) is the most commonly used pretreatment method for plasma spraying to roughen substrate surfaces. Howev
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