분말 사출 성형법으로 제조된 T42 고속도 공구강의 소결 조건에 따른 조직 특성 변화

Abstract

High speed steels (HSS) were used as cutting tools and wear parts, because of high strength, wear resistance, and hardness together with an appreciable toughness and fatigue resistance. Conventional manufacturing process for production of components with HSS was used by casting. The powder metallurgy techniques were currently developed due to second phase segregation of conventional process. The powder injection molding method (PIM) was received attention owing to shape without additional processes. The experimental specimens were manufactured with T42 HSS powders (59 vol%) and polymer (41 vol%). The metal powders were prealloyed water-atomised T42 HSS. The green parts were solvent debinded in normal n-Hexane at 60oC for 24 hours and thermal debinded at N2-H2 mixed gas atmosphere for 14 hours. Specimens were sintered in N2, H2 gas atmosphere and vacuum condition between 1200 and 1320oC. In result, polymer degradation temperatures about optimum conditions were found at 250oC and 480oC. After sintering at N2 gas atmosphere, maximum hardness of 310Hv was observed at 1280oC. Fine and well dispersed carbide were observed at this condition. But relative density was under 90%. When sintering at H2 gas atmosphere, relative density was observed to 94.5% at 1200oC. However, the low hardness was obtained due to decarbonization by hydrogen. In case of sintering at the vacuum of 10-5 torr at temperature of 1240oC, full density and 550Hv hardness were obtained without precipitation of MC and M6C in grain boundary.