Deposition Features of Ti Coating Using Irregular Powders in Cold Spray
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Shuo Yin, Pengjiang He, Hanlin Liao, and Xiaofang Wang (Submitted January 10, 2014; in revised form May 4, 2014) The investigation on the deposition features of irregular Ti powders coated on Al and stainless steel (SS) substrates was conducted in this study. Ti coating was experimentally produced at different gas inlet temperatures, and then detailed analysis on the critical velocity, coating microstructure, porosity, and microhardness was performed. As an assistant method, numerical simulation was also adopted to study the deformation features of single-irregular Ti particle during the cold spray process. The results reveal that the critical velocity of Ti particle on Al substrate is higher than that on SS substrate due to the different substrate hardness. The coating porosity is shown to be decreasing as the inlet temperature increases and independent to the substrate material. Similar phenomenon is also noticed for coating microstructure, but the changing trend is reverse in this case. Finally, the most important finding is that an additional torque imposed on the irregular particle is generated during the deposition process, which tends to detach the bonded particle from the substrate surface.
Keywords
cold spray (CS), deposition, numerical simulation, particle deformation, substrate hardness, titanium (Ti)
1. Introduction Cold spraying (CS), also called cold gas dynamic spraying (CGDS) or kinetic spraying (KS), is a relatively new coating technique developed in the mid-1980s and has been rapidly developing during the past two decades. In this process, powder particles are accelerated to a high velocity normally ranging from 300 to 1200 m/s in a supersonic jet flow and projected onto the substrate or already deposited coating at an entirely solid state. The ‘‘low temperature’’ in CS process can minimize the adverse effect brought by molten or semi-molten state, providing a possibility to coat oxygen-sensitive materials. Generally, particle velocity prior to the impact is an important factor that determines whether particles can adhere on the substrate surface. It has been widely accepted that there exists a material-dependent critical velocity for a given condition (e.g., specific particle size, temperature, and material Shuo Yin, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China and Laboratoire dÕEtudes et de Recherches sur les Mate´riaux, les Proce´de´s et les Surfaces (LERMPS), Universite´ de Technologie de Belfort-Montbe´liard, Site de Se´venans, 90010 Belfort Cedex, France; Pengjiang He and Hanlin Liao, Laboratoire dÕEtudes et de Recherches sur les Mate´riaux, les Proce´de´s et les Surfaces (LERMPS), Universite´ de Technologie de BelfortMontbe´liard, Site de Se´venans, 90010 Belfort Cedex, France; and Xiaofang Wang, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
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