Effect of substrate bias on microstructure and properties of nitride coatings on 304 stainless steel

304 stainless steel is susceptible to pitting corrosion failure in severe marine environments. Surface protective coating technology acts as one of the effective methods to extend its service life. Transition metal nitride coatings possess great application potential owing to their high hardness, excellent wear resistance and superior corrosion resistance. Compared with simple binary coating systems such as TiN and CrN, multicomponent multilayer coatings can further improve protection performance via element doping, structural design and precise interface regulation. The fabrication of multicomponent multilayer coatings is relatively complicated. Variation in process parameters, including bias voltage, gas flow rate and sputtering power exert significant influences on coating properties, and improper parameter control leads to rapid degradation of coating performance. In this work, four-layer TiCrAlSiN/Ti coatings with an overall thickness of approximately 3.9 μm were deposited on 304 stainless steel substrates by magnetron sputtering under substrate bias voltages of -100, -130, -160 and -190 V. The effects and internal mechanism of substrate bias voltage on the microstructure evolution, hardness, elastic modulus, coating-substrate adhesion and corrosion resistance of the prepared coatings were systematically investigated. The results show that coatings deposited under low substrate bias voltage exhibit unsatisfactory hardness, elastic modulus and corrosion resistance, and no prominent strong fiber texture can be observed. When the substrate bias voltage increases to -160 V, the coating presents a hardness of 37.36 GPa and an elastic modulus of 344.32 GPa, accompanied by the formation of a strong fiber texture. The maximum central texture intensity of the (111) plane from the pole figure reaches 7.42. Under this preparation condition, the coating obtains the maximum corrosion potential of -0.043 V and the minimum corrosion current density of 0.020 μA/cm².And delivers the optimal corrosion resistance and comprehensive performance. Further elevation of the substrate bias voltage reduces the hardness and elastic modulus of the coating, weakens texture intensity and deteriorates corrosion resistance. This work clarifies the influence of substrate bias voltage on the hardness, elastic modulus and coating-substrate adhesion of four-layer TiCrAlSiN/Ti coatings, as well as its regulatory effect on coating microstructure especially fiber texture. The internal mechanism by which substrate bias voltage affects the corrosion resistance of the coating is further revealed. The research outcomes provide vital experimental and theoretical support for the design and process optimization of high-performance protective coatings applied in marine service environments.