Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
2 results
Search Results
Item An Assessment of Coating Thickness on the Microstructure and Mechanical Behavior of IN625 Coating on Ni-Based Superalloy Substrate Deposited by High Velocity Air Fuel Technique(Springer, 2024) Prashanth, M.; Babu, N.; Kumari, S.; Maurya, S.S.; Keshri, A.K.; Cadambi, S.; Nand Gosvami, N.N.; Bhowmik, A.High velocity air fuel (HVAF) technique, an innovative thermal spraying method, has proven more promising than traditional methods for both coating and repairing surfaces. This study focuses on the application of different thicknesses of IN625 superalloy coatings using HVAF to assess its potential for repair and cladding applications. Detailed coating characteristics of IN625 superalloy coating have been examined based on various techniques like nanoindentation, adhesion, micro-tensile and flexural strength of the coated samples. Within the coating, ? (NiCr rich), secondary peaks ?? and carbide phases were identified. Particle deformation under impact and rapid cooling resulting in the formation of ?? precipitates enhances the coating strength. However, the decrease in the adhesion strength with increasing coating thicknesses results from the defects formed at the coating–substrate interface and also influenced by thermal stresses and oxidation. Coating microstructure revealed a strong particle-to-substrate adhesion and varied splat morphologies dependent on degree of particle melting—at higher particle velocities in-flight oxidation of the powders was also minimal. Furthermore, the in-plane cohesive strength of the coating approaches 50% of the wrought alloy's yield strength, attributed to strain hardening from the peening effect. However, decrease in flexural strength as coating thickness increases due to compressive residual stress and coating delamination. The flexural strength of the as-sprayed coating exhibits up to 70% of the flexural strength of the wrought material with thicker coatings exhibiting lower strength. © ASM International 2024.Item Mechanical and Tribological Properties of High Velocity Air Fuel-Sprayed IN625 and IN718 Coatings(Springer, 2025) Kumari, S.; Raj, S.; Babu, N.; Prashanth, M.; Junaid, S.; Cadambi, S.; Mondal, C.; Nand Gosvami, N.N.; Bhowmik, A.This study explores the mechanical and tribological behavior of IN625 and IN718 coatings deposited on Ni-based IN718 alloy substrates using the high-velocity air fuel, HVAF technique. Microstructural analysis revealed that the IN625 coating exhibited more visible splats, weaker bonding, and a greater presence of unmelted and partially melted regions than IN718. Both IN625 and IN718 coatings retained the original constituent phases from the powder. The IN718 coating, however, demonstrated superior mechanical properties, with its hardness and adhesion strength surpassing those of IN625 by 56% and 30%, respectively. Notably, the adhesion strength was highest in a 0.5 mm thick IN718 coating, reaching 63 MPa. At room temperature, both the coatings had significant coefficient of friction (COF) values, while the wear volume loss for IN718 was reduced by 52% compared to IN625, although IN625 showed wider wear scars with more pits, deeper grooves, and peeling. IN718 formed a glaze layer, enhancing its wear resistance. These findings suggest that optimally thick IN718 HVAF coatings hold significant promise for improving performance in various repair and cladding applications. © ASM International 2025.