Title: Effect of aluminising on the low cycle fatigue life of a directionally solidified nickel-base alloy used for manufacturing turbine blade

Authors: Benudhar Sahoo; S.K. Panigrahi; Shri R.K. Satpathy

Addresses: Regional Centre for Military Airworthiness (Koraput), CEMILAC, DRDO, Odisha, India ' Department of Mechanical Engineering, Defence Institute of Advanced Technology (Deemed University), Girinagar, Pune-411 025, India ' Regional Centre for Military Airworthiness (Koraput), CEMILAC, DRDO, Odisha, India

Abstract: In the recent years, directionally solidified (DS) turbine blades are found widely in advanced aero-engines owing to their excellent creep resistance properties. Aluminising coating on turbine blades protects against high temperature oxidation and corrosion. Turbine blades of a military gas turbine engine are subjected to low cycle fatigue (LCF) damage during START and STOP cycles. The present investigation deals with the low cycle fatigue (LCF) life of a directionally solidified nickel-base super alloy MAR M 002. Influence of aluminising on LCF life of the DS alloy MAR M002 has been evaluated by carrying out strain controlled LCF test at 900°C with strain amplitudes (Δεt/2) of ±0.3%, ±0.5%, and ±0.8% at a strain ratio (R) of −1. At low strain, coating favours LCF life. Accumulated plastic strain and tensile stress developed during cyclic loading and stiffness ratio are being used to correlate fatigue life. Fractography revealed initiation of cracks in the coating and multiple secondary cracks.

Keywords: low cycle fatigue; LCF; directionally solidified; DS; aluminising; diffusion; fractography.

DOI: 10.1504/IJMSI.2018.093894

International Journal of Materials and Structural Integrity, 2018 Vol.12 No.1/2/3, pp.58 - 75

Available online: 24 Jul 2018 *

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