The Control of Solidification of Ni‐Based Superalloy Single‐Crystal Blade by Mold Design Modification using Inner Radiation Baffle

Abstract

This work is focused on an investigation of the directional solidification process of CMSX‐4 single‐crystal blades in the mold modified by application of inner radiation baffle (IRB). Micro‐ and macrostructure examination is carried out along the height of single‐crystal blades which are manufactured using standard and modified mold, at the withdrawal rates of 3 and 5 mm min−1. It is established that application of modified mold allows better control over liquidus isotherm and leads to increase in temperature gradient, as compared to the manufacturing of blades using standard mold. The average value of temperature gradient in airfoil increases from 14 up to approx. 30 K cm−1 and from 16 up to approx. 40 K cm−1, for withdrawal rate of 5 and 3 mm min−1, respectively. The curvature of liquidus isotherm diminishes and attains near‐flat profile along the airfoil for both values of withdrawal rate. The application of proposed technique results in reduction of primary dendrites arm spacing (PDAS) particularly in the inner and middle part of the blade. PDAS reaches average value of approx. 360 μm for withdrawal rate of 5 mm min−1 and is lower as compared to the standard mold casting withdrawn at the rate of 3 (433 μm) and 5 mm min−1 (468 μm).