Simulation study of temperature distribution and cooling process optimization in internal diameter atmospheric plasma spray

Abstract

Heat accumulation and poor particle deposition during internal diameter atmospheric plasma spray (ID-APS) adversely affect the gun and coating performance. A cooling process could mitigate these negative effects, but it may cause the plasma jet to deflect. Therefore, a more effective cooling method with less impact on the jet needs to be investigated. This study analyzes the temperature, velocity and particle distribution fields during spraying inside cylinders. The effects of cylinder diameter and cooling airflow on temperature distribution and particle behavior in ID-APS were investigated. As the cylinder diameter decreases, the environment temperature and plasma jet temperature within 5 mm of the substrate increase significantly, leading to an increase in temperature during the deposition of 1–20 μm particles. The backflow formed due to the enclosed wall jet increases the edge velocity of the plasma jet, and then particles around 10 μm are more easily deflected from the plasma jet. Due to the relative position between the enclosed wall jet and the gun, the temperature is higher at the sides of the gun. As the cylinder diameter decreases from 130 mm to 70 mm, the highest temperature area moves from the back side to the front side of the gun. The cooling airflow introduced on both sides of the plasma jet effectively reduces the environment temperature. However, the excessive rate of airflow significantly deflects the jet near the substrate, which increases the dispersion of the particle deposition location and temperature-velocity distribution.