Among hardfacing processes using welding, laser cladding is nowadays one of the most efficient surface coating techniques. It is widely used to increase wear and corrosion resistance of machine parts as a result of the unique process characteristics such as low heat input (smaller heat affected zone), distortion free clad layers, lower dilution rate, finer coating microstructure as well as good metallurgical bonding at the coating/substrate interface. A wide range of new hardfacing materials and corrosion-resistant alloys are available on the market and in this study, different coatings of Ni-, Co- and Fe-based alloys as well as carbide-based metal matrix composites have been deposited by laser cladding for benchmarking purposes. Coatings were deposited onto mild steel substrates using a high-power diode laser. Coating microstructure and hardness were investigated as well as their tribological properties such as 2-body and 3-body abrasion, slurry abrasion and cavitation erosion resistance. Corrosion performance of coatings was also investigated with the salt spray test. Coatings are ranked according to their performance in the different tests and relationships between microstructure and coating properties are discussed.

Abradability, erosion and steam oxidation tests were conducted on commercial and experimental abradable coatings in order to evaluate their suitability for applications in steam turbines. Steam oxidation tests were carried out on free-standing top coat samples as well as coating systems consisting of a bond and an abradable top coat. Mapping of the abradability performance under widely varied seal strip incursion conditions was carried out for a candidate abradable coating that showed good steam oxidation performance in combination with good erosion resistance. The abradability tests were carried out on a specially designed test rig at elevated temperatures. The steam oxidation analysis combined with the abradability mapping results provide a potentially improved seal coating system that can be integrated into existing steam turbine designs for various seal locations. Such design integration is easily achieved and can be applied to steam turbine components that are sprayed in dedicated coating shops or even at the site of final turbine assembly.