Titanium carbide/duplex stainless steel (DSS) metal matrix composite coatings prepared by the plasma transferred arc (PTA) technique: microstructure and wear properties

The present investigation focuses on the microstructure and the tribological properties of TiC/steel composite coatings obtained on 2205 duplex stainless steel (DSS) substrate, by using the plasma transferred arc technique. Two different plasma and shielding gas mixtures have been used, namely (a) 100% Ar and (b) 95% Ar + 5%N₂. The coatings obtained are defect-free and their thickness is 1.50 ± 0.05 mm. Both coatings consist of a dispersion of TiC _x N _y particles, with a volume fraction of about 18–22%, in an austenite–ferrite matrix. The austenite-to-ferrite volume fraction is 35/65% for the Ar coatings and it is found to increase to 40/60%, when nitrogen is used in the plasma and shielding gas. The hardness of the composite coatings is improved significantly (630–650HV on average) compared to the hardness of the substrate (250HV). The friction coefficient produced against an Al₂O₃ counterbody has decreased considerably to 0.2–0.3 from 0.5 for the 2205/Al₂O₃ pair and the wear rate was reduced at least by one order of magnitude with respect to the value of the 2205 DSS substrate.