Development of a closed-loop control system for laser-directed energy deposition (L-DED) of stellite alloy

Abstract

Laser-Directed Energy Deposition (L-DED) of superalloys like Stellite-21 is widely used in aerospace, defence and energy industries for precision repair, cladding, and restoration of high-value components. Stellite-21, a cobalt-chromium-molybdenum alloy, offers excellent high-temperature wear resistance and chemical stability, making it ideal for turbine blade repair and engine component refurbishment. However, achieving consistent geometric accuracy, dimensional stability and defect free deposition remains a fundamental challenge. The principal causes are highly nonlinear thermal effects, standoff-drift, laser-material interaction & dynamic melt pool emissivity. This thesis presents the design, development and experimental validation of a real time, three pillar closed loop control system for L-DED of Stellite-21 deployed on the TVASHTR five axis L-DED facility at the RRCAT, Indore.