Simulation of Dual Microstructure Heat Treatment Process and Residual Stresses in Gas Turbine Disc by DeformHT Software

Abstract

Gas turbine disc is one of the most vital components in advanced gas engine. In order to improve the tensile strength and fatigue strength of the disc, finer grain size is to be attained at bore area and coarser grain structure at rim area in order to resist the growth of creep. Attempts have been made by several researchers experimentally on the development of dual microstructure for Inconel-718 by heat treatment technique. However, the simulation of induction and resistance heat treatment process to achieve dual grain size and reduce residual stresses is not yet reported. In the present work, an attempt is made to obtain the optimal induction heat treatment process parameters to achieve the dual grain structure at bore area and estimate the residual stresses to predict the disc performance. The induction heat treatment process is simulated using DEFORMHT software to achieve dual grain size of 5.6 μm at bore area and 46.3 μm at rim area of the disc. The rim area of the disc was heated to 1080ºC with varying input power from 10 to 30 kW at frequency 20 kHz. The disc was soaked for 60 min at a constant temperature of 1080ºC and then cooled at a rate of 1ºC/min to room temperature. The disc with induced residual stresses was further subjected to heating at 700, 800 and 900ºC. Reduction in residual stresses was finally achieved by soaking the disc at three intervals (3600, 7200, and 1800 s). Grain size achieved after and before resistance heat treatment was measured by obtaining state variable method in DEFORMHT software).

Cite this Article

Adarsha H, Ramesh S, Prasad Kaushik

V et al. Simulation of Dual

Microstructure Heat Treatment Process

and Residual Stresses in Gas Turbine

Disc by DeformHT Software. Journal of

Materials & Metallurgical Engineering.

2017; 7(1): 30–42p.