The role of superimposing pulse bias voltage on DC bias on the macroparticle attachment and structure of TiAlN coatings produced with CA-PVD

Our attempts for cathodic arc physical vapor deposition (CA-PVD) of TiAlN coatings with high voltage pulse bias in order to tune their structural properties were not successful. Resulted coatings had an unacceptable rough surface with a large number of macroparticles (MPs). For solving this problem and benefiting from high voltage pulse bias-induced effects on the coatings structure we superimposed high voltage pulse on DC bias. For this purpose, Ti0.5Al0.5N coatings were deposited on HSS substrates using a DC bias voltage of 40 V and superimposed pulse bias voltages of 500, 1000 and 1500 V with a duty cycle of 14%. Structure, chemistry, morphology and mechanical properties of the coatings were determined in order to investigate the differences induced by the application of superimposed bias. Additionally, corrosion protection properties of the coatings were also investigated. According to the obtained results, this mode of application not only produced coatings with a denser and finer columnar structure but also resulted in a substantial reduction in the number of MPs. A decrease (maximum 3 at.%) in the Al content of the coatings was observed with increasing pulse bias magnitude when compared to their DC bias deposited counterpart. Substrate temperature also increased with increasing pulse bias magnitude, however, it did not increase above 460 °C. As a result of the decrease of MP attachment and denser structure of the coatings the corrosion protection properties of the coatings substantially improved. This effect became more pronounced with increasing superimposed voltage magnitude.