Influences of the ID-HVOF Process Parameters on the Properties of Cr3C2-NiCr-75/25 Linings

The lining of inner surfaces by means of internal-diameter high-velocity oxy-fuel (ID-HVOF) spraying is becoming increasingly significant in research and industry. Due to various boundary conditions, the investigation of the process parameters with regard to their influences on high-quality linings is proving to be more complex than in the case of outer-diameter (OD) coatings. These conditions include the limited movement space for torches and peripheral devices, narrower parameter ranges as well as restricted possibilities for the cooling and extraction of spraying dusts. Decisive importance is attached to establishing the significance of individual process parameters for the lining process as well as of the resulting lining properties in order to permit comprehensive optimisation. Furthermore, the application of alternative carbide linings (cermets: ceramic metals) for the most widely used WC-CoCr lining system is of particular interest. Precisely in view not only of the availability of WC (critical material) but also of health-related aspects of Co, great interest is centring on the systematic development of high-quality Cr3C2-NiCr-75/25 linings as well as on knowledge about the effects of relevant process parameters. One initial approach is being offered by statistical test planning on the basis of a central-composite-design (CCD) test plan which was carried out in the course of the IGF 22.829N project. For this purpose, pilot tests using a Cr3C2-NiCr-75/25 spraying powder were performed in the first step. The CCD test plan was set up using the resulting parameter range.