Microstructure and Morphology Analysis of DC-Magnetron Sputtered TiAlSi Thin Coatings on Glass, T42 High Speed Steel, and AISI 01 Tool Steel Substrates

This study investigates the properties of the base coating, TiAlSi, which is often used in reactive sputtering for surface protection of conventional tool materials for machining operations. The TiAlSi thin film coatings were deposited on glass, T42 High-Speed Steel (HSS), and AISI 01 Tool Steel (TS). TiAlSi thin films are deposited by Direct Current (DC) Magnetron Sputtering (DCMS) using a custom-made Ti52Al16Si10 wt.% target using a range of substrate temperatures (23–400 °C) and deposition times (40–190 minutes). The thickness of the thin films significantly reduces from about 252 nm to 122 nm with an increase in the substrate temperature from 23 °C to 400 °C, respectively. The topographic and microstructural analyses show large and flattened particles of TiAlSi thin films on coatings deposited for longer periods (at 150 and 190 minutes) and a reduction in the physical grain sizes with increased substrate temperature, hence the reduced coating thickness. High-temperature deposition of TiAlSi coatings on HSS and TS leads to the development of troughs, hillocks, and craters as the major forms of defects, which ultimately increase the roughness values of the thin films. Analysis of the crystal structure of the as-deposited TiAlSi coatings shows the amorphous nature of the coatings with no observable peaks. These findings allow for the precise tailoring of the deposition parameters of TiAlSi thin films as base coatings for Ti-based thin films for surface protection of cutting tools.