코어-쉘 복합분말을 통해 미세조직이 제어된 Mo-Si-B합금의 제조

Abstract

초고온 재료는 항공 분야 및 발전 분야에 사용되는 고온용 가스 터빈 엔진의 효율을 향상시키기 위해 주로 개발되어왔다. 현재 가스 터빈 엔진의 재료로 사용되는 Ni기 초내열 합금은 융점의 약 90%인 약 1150℃까지 사용될 수 있는 상황이다. 이러한 가스 터빈 엔진의 효율을 향상시키기 위해서는 더욱 높은 온도에서 사용될 수 있는 재료의 개발이 요구된다. 최근 Mo-Si-B 합금은 Ni기 초내열합금의 대체재료로 각광 받고 있다. Mo-Si-B 합금은 내산화성 및 기계적 특성이 우수한 장점이 있기 때문에 Ni기 초내열 합금이 한계에 있는 온도수용성의 향상이 가능하며, 이를 통해 가스터빈의 효율이 증가할 것으로 예상된다. 하지만 이러한 Mo-Si-B 합금은 실제적용에 필요한 일정 수준의 인성이 부족한 단점이 있으며, 이의 극복을 위해서는 미세조직 내에 연속적인 형태의 α-Mo상 기지를 형성함으로써 인성을 향상시키는 노력이 필수적이다. Mo-Si-B 합금을 제조하는데 있어서, 기존 방법들은 원하는 미세구조를 제어하기 어려운 단점이 있었다. 따라서, 본 연구는 새로운 분말야금 공정을 도입하고자 하였다. 기계화학적 공정을 이용하여 MoO3, Si3N4, BN의 시작분말로부터 Mo5SiB2, Mo3Si 상이 혼재하는 금속간화합물 분말을 제조하였으며, 금속간화합물-Mo의 코어-쉘 복합분말의 제조를 통해 최종적으로 원하는 미세조직을 갖는 3상의 Mo-Si-B합금을 제조하였다.|Ultrahigh temperature materials have been mainly investigated to improve the efficiency of aerospace and power-generation gas-turbine engines operating at high temperatures. Currently, turbine blades of Ni-based superalloys can be used at temperatures up to 1150℃, which is close to 90% of their melting points. . In order to achieve better efficiency of gas-turbine engines, the development of materials applicable at higher temperature is required. Recently, Mo-Si-B alloys have attracted attention as a potential materials for gas-turbine engine due to their high melting points(>2000℃) and excellent oxidation resistance as well as mechanical properties at high temperature. However, Mo-Si-B alloys have poor fracture toughness for actual application. An effort of improvement in toughness by forming the microstructure with continuous α-Mo phase is essential to overcome disadvantage of this alloys. In previous study, existing methods for fabrication had a limit on controlling the required microstructure. In this study, therefore, a novel powder metallurgy method is applied. Finally, three phases Mo-Si-B alloys with required microstructure were fabricated by mechano-chemical process from MoO3, Si3N4 and BN as starting powders to synthesis of intermetallic powders including Mo5SiB2 and Mo3Si and fabrication of intermetallic-Mo core-shell composite powder.; Ultrahigh temperature materials have been mainly investigated to improve the efficiency of aerospace and power-generation gas-turbine engines operating at high temperatures. Currently, turbine blades of Ni-based superalloys can be used at temperatures up to 1150℃, which is close to 90% of their melting points. . In order to achieve better efficiency of gas-turbine engines, the development of materials applicable at higher temperature is required. Recently, Mo-Si-B alloys have attracted attention as a potential materials for gas-turbine engine due to their high melting points(>2000℃) and excellent oxidation resistance as well as mechanical properties at high temperature. However, Mo-Si-B alloys have poor fracture toughness for actual application. An effort of improvement in toughness by forming the microstructure with continuous α-Mo phase is essential to overcome disadvantage of this alloys. In previous study, existing methods for fabrication had a limit on controlling the required microstructure. In this study, therefore, a novel powder metallurgy method is applied. Finally, three phases Mo-Si-B alloys with required microstructure were fabricated by mechano-chemical process from MoO3, Si3N4 and BN as starting powders to synthesis of intermetallic powders including Mo5SiB2 and Mo3Si and fabrication of intermetallic-Mo core-shell composite powder.