The effect of renewed melting process under electrical slag on the fatigue life of the precipitation hardened stainless steel Custom-450

Abstract

The aim of this study was to investigate the effect of under electro slag re-melting (ESR) process on the fatigue behavior of GTD-450 steel used for manufacturing gas turbin blades. These parts are always at risk of failure due to fatigue. Refining of steel by ESR process is one of the most important modern methods of steelmaking in order to achieve a homogeneous structure, minimal elemental and structural segeregation, as well as reducing non-metallic impurities in terms of their number and size and most importantly their uniform distribution in the steel structure. Due to dependency of fatigue properties of steels on structural factors of steel, the role of ESR process using different slag compositions on this important property of GTD-450 steel was investigated. Microstructural studies by optical and electron microscopes showed that grain size of ESR samples were averagely 10% finer than non-ESR ones. As well as performing various mechanical tests including tensile and fatigue on samples prepared in different conditions, showed that although ESR had a minor effect on tensile properties of steel but impact energy of steel in ESR condition were averagely 16% more than non-ESR condition. Finally, the core finding of this paper is that, fatigue life of GTD-steel turbine blade produced via ESR method can be improved by 30%.

Keywords

• GTD-450
• Fatigue
• ESR
• Non-metallic impurities