Design Of Plasma Spraying Torch Of Powder Injected In Inside

Thermal plasma spraying is one of the important technologies in modern surface engineering. Thermal plasma spraying can obtain the coatings of high quality for its superior characteristics of high-temperature and high-velocity. Generally, in the traditional plasma spraying, the powders were injected into the plasma jet from outside the nozzle. So the power consumption is large, but the powder deposition rate is low. In allusion to such condition, we designed a set of new plasma spraying gun. The powders were injected into the plasma jet from inside the nozzle, so the powders were heated adequately and were sprayed in the plasma spraying direction to base surface. In 40~ 60kW power condition, it can spray metal and ceramics, and its efficiency was high. Due to the powders injection from inside the nozzle, it improved heat efficiency, at the same time, increased powder deposition rate.This paper introduced the design of plasma torch, and simulated the jet's capability in powder outside, inside and center condition, and it concluded that the plasma jet in inside had better quality and was designed not difficultly. It researched column nozzle, constringency—expand nozzle , Laval nozzle, bell nozzle and stepped nozzle's influence for jet, and concluded that the ladder nozzle's design and manufacture was easy, and its structure and quality suited with the jet. A new tungsten pole seat was designed. Generally, tungsten pole seat was brazed welding. If tungsten pole was burned loss, it must be replaced. It was extravagant. But our structure can adjust smartly tungsten pole's direction. When tungsten pole was burned loss, it can be knocked down, then burnished to needed shape. It can improve tungsten pole's use rate.Through simulation about jet powder inside, we can summarize its excellence: its powder splash rate was low, and it can save material. The jet can spray not only generalmaterial but also expensive and rare material. Also, the jet's heat enthalpy was high, so its heat efficiency was high. Then the jet powder inside in low power can reach the spraying effect which was reached by jet powder outside in higher power. It can save material and energy. In virtue of its high heat rate, the particle powder inside easily formed metallurgy combine in base surface, and coating strength and hardness was higher more than it powder outside.