이온질화된 공구강 표면의 산화 및 공식거동

Abstract

SKD11 steel has been widely used for tools, metallic mold and die for press working because of its favorable mechanical properties such as high toughness, and creep strength as well as excellent oxidation resistance. The ion nitrided tool steel containing Mo results in improvement of corrosion resistance, and strength at high temperature and pitting resistance, especially in Cl- contained environment. But the Mo addition causes a disadvantage such as lower oxidation resistance at elevated temperature. In this study, several effects of ion-nitriding on the oxdation characteristics for SKD11 steel with various oxidation temperature were investigated. SKD11 steels were manufactured by using vacuum furnace and solutionized for 1hr at 1,050oC. Steel surface was ion nitrided at 500oC for 1hr and 5hr by ion nitriding equipment. Ion nitrided specimen were investigated by SEM, OM, and hardness tester. Oxidation was carried out by using muffle furnace in air at 500oC, 700oC and 900oC for 1hr, respectively. Oxidation behavior of the ion nitrided specimen was investigated by SEM, EDX and surface roughness tester. The conclusions of this study are as follows: It was found that plasma nitriding for 5hr at 500oC, compared with ion nitriding for 1hr at 500oC, had a thick nitrided layer and produced a layer with good wear and corrosion resistance and hardness as nitriding time increased. Nitrided SKD11 alloy for 1hr showed that wear resistance and hardness decreased, whereas surface roughness increased, compared with nitrided SKD11 alloy for 5hr. The oxidation surface at 900oC showed a good corrosion resistance.