Fatigue Bending Behavior of Cold-Sprayed Nickel-Based Superalloy Coatings

Abstract

Cold-sprayed Ni-based superalloy coatings offer new possibilities for manufacturing and repairing damaged components, such as gas turbine blades or other parts of aircraft engines. This development shines a new light on the conventional additive manufacturing technologies and significantly broadens application fields of cold spray. The idea is that cold spray can contribute to improving the fatigue properties of manufacturing and repaired components. This study deals with the analysis of the microstructural and mechanical properties of IN625 cold-sprayed coatings on V-notched carbon steel substrate. Process conditions of 1000 °C and 50 bar were employed to produce coatings in V-notched (60° and 90°) samples in order to evaluate the fatigue crack behavior of the sprayed material. Bending tests were carried out in order to evaluate the crack propagation in the coatings during cyclic loading. The K factor was quantified for the two different notch geometries. After fatigue tests, the cracking mechanisms were observed through SEM. Optical microscopy, nanoindentation as a function of coating/substrate distance and corrosion tests were performed. Porosity measurements through image analyses were done to characterize the coatings’ quality. The results achieved demonstrate that cold spray deposition and repair can contribute to resistance and to the increase in the global fatigue life of cracked structures.