Hot corrosion is a critical problem in a wide range of high-temperature applications. Ni–20Cr alloy is frequently used in such applications owing to its good hot-corrosion resistance. In the current work, thick Ni–20Cr plates in a thickness range of 6–10 mm were fabricated using cold spray-based additive manufacturing (CSAM). High-pressure cold spraying was used with nitrogen as the propellant gas. Pre- (substrate heating, SH) and post-heat treatments (hot isostatic pressing, HIP) were also performed to comprehend the changes in the deposit properties. The deposits were subjected to microstructural and mechanical characterization to explore the potential of cold spraying for CSAM of Ni–20Cr standalone products. The cold-sprayed plates were successfully developed without any oxide formation. HIP treatment was found to be useful to reduce porosity. The cold-sprayed substrate-heated Ni–20Cr deposits exhibited excellent oxidation resistance at a high temperature of 900 °C.

In this work, thick deposits of pure titanium (Ti), with a thickness of around 15 mm, were additively manufactured using high-pressure cold spraying. Nitrogen was employed as the process gas. Subsequently, the deposits were subjected to hot isostatic pressing (HIP). The HIP-treated Ti deposits were analyzed for their metallurgical and mechanical characteristics with the aim of exploring the viability of using cold spraying for the additive manufacturing of Ti components. Moreover, high-temperature cyclic oxidation testing was also performed on the HIP-treated Ti deposit to understand its stability at high temperatures. SEM/EDS showed a dense structure with marginal porosity for the HIP-treated Ti deposits, without any oxide formation, which was further confirmed via XRD analysis. An average microhardness of 214 HV was measured for the HIP-treated Ti deposits, which is close to that of the commercially available bulk titanium (202 HV). The high-temperature oxidation studies revealed that the cold-sprayed HIP-treated Ti has very good oxidation resistance, which could be attributed to the formation of protective titanium dioxide in its oxide scale.

Cold Spray is an emerging technology in the domain of additive manufacturing. It is a solid-state high strain rate material deposition technique. It uses a supersonic (2-4 Mach) impact of process gas (such as nitrogen or helium) to deposit micron-sized (1-100 µm) metallic or composite powder particles onto a substrate via a severe plastic deformation mechanism without any significant fusion. To have a successful deposition, the specific powder particles should travel above a material-dependent threshold velocity, which is called the critical velocity. The convergent-divergent nozzle is employed for achieving high velocities. The main objective of the current research is to study the flow visualization of two-phase titanium particle laden nitrogen gas in a simulated 2-D axisymmetric nozzle where particles are having a particle size of 25 microns, and to investigate the suitability of a specific set of cold spraying process parameters for the successful deposition of titanium powder using computational fluid dynamics. For the analysis, a twoequation realizable k-ε simulation viscous model was preferred due to its more realistic consideration of the cold spray process and reduced computational cost. Titanium powder particles will be successfully deposited using cold spray when operated at the precise set of process conditions on account of the average particle velocity observed at standoff distance higher than the critical velocity.