Investigation on the removal of suspended particles during internal rotating plasma spraying using numerical and experimental methods

• Published in: Surface & coatings technology Vol. 393; p. 125731
• Main Authors: Ding, Shu-yu, He, Peng-fei, Ma, Guo-zheng, Wu, Zhi-yong, Tang, Ling, Chen, Shu-ying, Xing, Zhi-guo, Wang, Hai-dou, Xu, Bin-shi
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.07.2020; Elsevier BV
• Subjects: Asynchronous motors; Automotive engines; Confined spaces; Engine cylinders; Experimental methods; Flow velocity; Inclusions; Mechanical systems; Numerical methods; Numerical simulation; Particle mass; Particle mass concentration; Plasma; Plasma jets; Plasma spraying; Pressure effects; Removal degree; Rotating plasmas; Rotation; Service life; Substrates; Suction; Velocity distribution; Particle mass concentration; Numerical simulation; Velocity distribution; Removal degree
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.125731

Internal rotating plasma spraying (IRPS) plays an important role in improving the properties and prolonging the service life of internal parts and components of mechanical systems. IRPS is conducted in the confined and semi-enclosed spaces at a spraying distance of 30–70 mm to coat the engine cylinders of automobiles or heavy equipment. Occasionally, particles cannot be appropriately treated in the plasma flow, and owing to several factors, the particles remain suspended in the air rather than being deposited onto the substrate. Consequently, the suspended particles are difficult to remove efficiently within the confined space, and can thus have severe effects on the properties of coatings, including porosities and inclusions. It is therefore essential to develop appropriate methods to avoid defects in the coating by removing suspended particles inside the cylinder. In this study, numerical simulations were conducted to investigate the flow-velocity field and particle-mass-concentration distribution within the cylinder. The flow-velocity and particle mass concentration in the cylinder space were analyzed under different working conditions that can induce different suction pressures driven by a three-phase asynchronous motor connected to the bottom of the cylinder by a suction tube. The results showed that the flow-velocity field is symmetrical along the axis of the cylinder and the mass concentration of particle is concentrated on the region from middle to bottom of the cylinder, under the effect of the suction pressure. In addition, the low-velocity and high-particle-mass-concentration regions are mainly located in the vicinity of the internal wall. Furthermore, the flow velocity was measured using a hot-wire-anemometer and the coating microstructure was observed using scanning electron microscope (SEM). We compared numerical simulation results and experimental measurements, which validated the flow-velocity field directly and the distribution of particle mass concentration indirectly. Based on the numerical results that consider the removal degree of suspending particles and the stability of the plasma jet, it can be determined that the optimal suction pressure is −100 Pa for decreasing dust pollution during the spraying process. •Numerical simulations and experiments are both used in the research.•The flow-velocity field is symmetrical along the axis centerline of cylinder.•The mass concentration of particle is concentrated on the region from middle to bottom of the cylinder.•The optimal suction pressure is −100 Pa for decreasing dust pollution problem.