Research Projects

Ni-based superalloys are commonly used in manufacturing turbine blades for high-temperature and high-pressure environments. These blades are designed to be single crystal structures, which can be produced through multi-blades attached through a single gating system or multi-stage single crystal turbine blades. However, the production of these blades faces issues such as freckle defects and low production efficiency due to slow processing. To address these issues, new designs of grain selectors have been developed to produce multi-stage casting of blades free of flaws. In 2021, DMRL-DRDO developed the first single-crystal high-pressure turbine for helicopter engines. The proposal aims to develop lab-scaled single-crystal blade manufacturing with an understanding of freckles in multi-stage blades. This involves designing and manufacturing a novel vacuum Bridgman furnace that can control cooling rate and pulling rate for low- to high-temperature melting alloys. Additionally, a liquid metal cooling system will be adapted to maintain a constant thermal gradient in the solidification zone. Optical techniques will be used to simulate the freckle study in multi-stage turbine blades, using transparent alloys to visualize in-situ convective flow in directional solidification setups. This study will provide critical Rayleigh number and crystal growth parameters to suppress freckles and a new grain selector design for single crystal growth in the main solidifying region. The modified grain selector design will be used to obtain parameters for defect-free multi-stage single-crystal turbine blades. This proposal has the potential to develop a single-crystal Ni-based alloy in multi-stages on a lab scale with critical criteria to suppress freckle defects, scaling up to an industrial scale.