Abstract
High velocity oxyfuel flame spraying (HVOF) has a great potential for replacing the low pressure plasma spraying (LPPS) process in most applications for hot corrosion protective MCrAlY coatings for turbine hot gas path parts. Compared to LPPS coatings, state-of-the-art HVOF sprayed MCrAlY coating systems feature competitive hot corrosion protective properties. Low HVOF facilities investment costs and a stable, easy process controlling are major advantages in terms of application. Besides hot corrosion protective single layers, MCrAlY coating systems are used as bond coats for ceramic thermal barrier coatings (TBC). But HVOF sprayed MCrAlY coatings show a comparatively low surface roughness which leads to a poor adhesion of the ceramic top layer, restricting the application area of HVOF. This paper deals with a development project which aims on roughness enhancement of HVOF sprayed MCrAlY coatings in order to improve the bonding properties of the TBC. In the project’s framework, several HVOF systems and different powders were investigated. Parameter sets were developed considering both a high surface roughness and a low level of defects in the coating.
