Cold Sprayed MCrAlX Bond Coats for Thermal Barrier Coatings Applications

MCrAlX powder compositions (M=Ni,Co and X=Y, Hf, Si or combinations) are thermally sprayed to produce high temperature oxidation and hot corrosion resistant bond coats (BC) for thermal barrier coatings (TBCs). In particular, the addition of Hf is meant to increase the adhesion of the thermally-grown oxide layer while TBCs are subjected to thermal exposures. In this presentation, we will discuss conventional cold spray (CS) and laser assisted cold spray (LACS) deposition of MCrAlX alloys such as NiCoCrAlY+HfSi through the use of both high and low-pressure CS systems, and compare their typical as-sprayed developed microstructures. We are showing that LACS can be successfully used to deposit MCrAlX bond coats with required thickness (e.g. 150-200um) while eliminating nozzle erosion and low deposition efficiency drawbacks observed with CS. Structural and phase characterization of the as-sprayed BCs were carried out by SEM, EDX and XRD analysis. The effect of surface roughness of the CS BCs on adhesion and microstructure of air plasma spray (APS) deposited yttria stabilized zirconia (YSZ) top coats is further presented. Isothermal exposure lifetime of these architectures is compared to that of TBCs having the MCrAlX BCs produced via air plasma spray.