In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.

This work is dedicated to the study and the characterization of the surface of nickel superalloys before the deposition of the MCrAlY (M_ Co, Ni or both) bond coat. Our aim is to determine the factors (roughness, contamination and others) that lead to the best properties of the coating in terms of adhesion. We used MAR M247 samples as substrates. Different preparation treatments were considered: dry and wet blasting by corundum with different grain size distribution, dry blasting by silicon carbide and cleaning by solid carbon dioxide. In general, we observed that the highest roughness led to the best adhesion as measured by critical load tests. However, this parameter must be balanced against known problems related to the use of coarse abrasive powders. ᮊ