Microstructures and properties of nanostructured thermal sprayed coatings using high-energy milled cermet powders

This study demonstrates the potential of high-energy milling to use nanostructured cermet powders for thermal spraying utilizing a TiC-Ni-based composite as model material. The microstructure of coatings processed by VPS and HVOF spraying of nanostructured composite powders is characterized and compared to the initial microstructure of the feedstock. Thus, the effect of different microstructures, which can be produced by high-energy milling, on the microstructural evolution during spraying is evaluated. Results show that partial dissolution and reprecipitation of hard phase material as well coarsening of the binder phase crystallite size occur during the spraying process. However, a homogeneously dispersed hard phase distribution similar to that of the nanostructured precursor powder with hard phase sizes in the range of 100 nm is formed. Additionally, hard phase particles bigger than of 300 nm are retained during spraying. First results concerning hardness and wear resistance of respective coatings are shown and discussed.