Nitriding of titanium plate and atmospheric plasma sprayed titanium coating using nitrogen plasma jets under a low pressure environment

摘要

Nitriding is a useful method to improve the heat, corrosion or wear resistance of metals. Hence, surface nitrided materials and nitride films have been successfully used for many applications. However, conventional nitriding processes, for example gas nitriding and plasma nitriding, have low nitriding rate, and it takes few hours to obtain practical surface nitrided materials or nitride films by using the above mentioned method. Therefore we thought nitriding process utilizing high reactivity of direct-current (DC) arc jet plasma in order to develop the nitriding process with high nitriding rate. DC arc jet, which is one of thermal plasma, has high energy density, many reactive species and high flux. However, since plasma jet is accelerated to supersonic flow under a low pressure environment, it encounters some significant problem which is adiabatic expansion, shock wave generation, frozen flow generation, and so on when reactivity of plasma jet is utilized.