벨브용 내열합금의 고온 수증기분위기하에서의 산화 특성 = Oxidatiion Characteristics of Heat Resisting Alloy for Valve in High Temperature Steem Environment

다국어 초록 (Multilingual Abstract)

Thermogravinetric measurement and oxide scale analysis have been done to study the oxidation behaviour of A335, A437 alloy and Nitrided A355, A437 in high temperature steam environment. When A335, A437, and Nitrided A335, A437 was oxidized under high temperature water vapor had been formed oxide scale consist of two layer structure. At all the temperatures parabolic kinetics was observed in the oxide scale formation, and its apparent activation energies were estimated to be 20.0kcal/mol for A335 and 61.05kcal/mol for A437, respectively. But apparent activation energies in case of Nitrided A437 and A355 alloy was 25.9kcal/mol, 16.68kcal/mol respectively. With the increase of Cr content in the alloys the oxidation rates decreased. The case of surface nitriding alloys was rather weakened high temperature water vapor resistance than non-nitirding alloy. The oxide scales of A437 alloy were identified as ??, ??, ??, ?? matrix form the surface. The oxide scales of A355 alloy were identified as ??, (Al, Cr, Fe)??, matrix from the surface.