코발트기 자융성 합금 코팅의 Tribology 특성에 관한 연구

Abstract

Since the surface of materials is directly exposed to the surrounding environment, wear and corrosion damage often occurs. In order to solve these problems, thermal spray technique is spotlighted in many industries. Especially, thermally sprayed Co-based self-flux alloy coating which has excellent wear and corrosion resistance is widely used in industries that require superior surface characteristics. As self-flux alloy is inherently designed for heat-treatment after forming the coating layer, defects of coating layer such as porosity, unmelted particle and splat boundary can significantly be reduced by heat-treatment. This paper describes process optimization for thermally sprayed Co-based self-flux alloy coating by Taguchi method and effect of heat treatment on tribology characteristics of Co-based self-flux alloy coating. Coating specimens were fabricated on steel substrates according to L9(34) orthogonal array using flame spray process. Microvickers hardness test and ball-on-disk type sliding wear test were performed. In order to derive the optimum process condition, the results were analyzed by analysis of variance(ANOVA) considering a multi response signal to noise ratio(MRSN). Heat-treatments were carried out at 800, 900, 1000 and 1100℃ for 30min in a vacuum chamber. For analysis of effect of heat treatment on tribology characteristics, wear test and hardness test were performed for heat-treated coating specimens. Microstructures of heat treated coating layer and wear track were examined using SEM and EDS. From the results of ANOVA, the optimal combination of the flame spray parameters on Co-based self-flux alloy coating could be predicted. The calculated hardness and wear rate of the coatings by ANOVA were found to be close to that of confirmation experimental result. In following study, effect of heat-treatment temperature on tribology characteristics of Co-based self-flux alloy coating was analyzed. The principal wear behavior of the as-sprayed coatings was splat detachment. However, dominant wear behavior of heat-treated coatings transferred to abrasive wear with increasing heat-treatment temperature.