Development of suspension plasma sprayed alumina coatings with high enthalpy plasma torch

Deposition of aluminium oxide (Al2O3) coatings from liquid feedstocks using a high enthalpy hybrid water-stabilized plasma torch was investigated. The entire process included the optimization of spraying parameters using a commercial ready-to-spray suspension, optimization and deposition of custom-made suspensions and one solution and evaluation of mechanical properties of the most durable coatings. Acquired coating microstructures varied from porous with typical columnar morphology to well-sintered dense structures with low porosity. The microstructural features were clearly linked to the feedstock formulation. The most durable coating with the highest density microstructure prepared from ethanol-based suspension showed outstanding mechanical properties, e.g. high values of hardness (up to 1211HV0.3), tensile adhesion strength (up to 51MPa) and wear resistance (material removal rate as low as 1.94·10−5mm3·N−1·m−1 as measured by pin-on-disc test). Moreover, deposition from a water-based solution of aluminium nitrate resulted in deposition of highly porous coating composed predominantly of stable α-alumina phase. •Optimized ready-to-spray suspensions suitable for WSP-H torch were developed.•Various microstructure types from porous to highly sintered compact were deposited.•Exceptional mechanical properties of the suspension-sprayed coatings were found.