Modeling and Experimental Analysis of Bias Voltage Effects on Hardness and Thickness of TiN Coatings Produced by PVD Process

This study examines the impact of bias voltage on the mechanical properties and film thickness of TiN coatings deposited on cold work tool steel via the PVD process. TiN coatings, known for their excellent hardness and wear resistance, were deposited at varying bias voltages (100–300 V). Hardness measurements and SEM analyses were conducted to evaluate the relationship between bias voltage, hardness, and film thickness. Theoretical models, including hardness-load and indentation hardness relationships, were developed to provide a comprehensive understanding of these trends. The results demonstrate that increasing the bias voltage enhances coating hardness up to 250 V due to improved atomic mobility and nucleation density. However, beyond this threshold, grain coarsening and defect formation contribute to a reduction in hardness. A monotonic decrease in film thickness was observed with higher bias voltages, attributed to ion bombardment and re-sputtering effects. The developed models showed strong alignment with experimental results, particularly for indentation hardness behavior, while discrepancies in the hardness-load relationship were noted under high loads and higher bias voltages. These findings underscore the importance of precise bias voltage control and theoretical modeling in enhancing TiN coating performance for industrial applications.