Understanding the Fatigue Response of Cold Sprayed Ni based Superalloy Coatings

The cold spray method of material deposition is widely used for surface enhancement. In many ways, it is seen as being akin to shot peening, a technique routinely used to enhance the fatigue life, in many structural engineering components, via inducing compressive residual stresses on the surface. However, in the case of cold spray coatings, there are contradictory results when it comes to the fatigue properties of the coated system, depending on the coating substrate combination. While some systems such as the aluminium on aluminium tend to show an enhancement in the fatigue properties, others such as the nickel based alloys, tend to show a decrement in the fatigue behavior. This study presents an understanding of the low cycle and high cycle fatigue response, of a few Ni- based superalloys, IN625 on 4130 steel, IN718 on CrMoV steel and MCrAlY on GTD111* alloys. The fatigue behavior has been studied, and correlations have been made with respect to the residual stress and microstructure of the coating – substrate interface, to explain the observed behavior.  *Trademark of General Electric Company