Improving the physicochemical surface properties on AISI D3 steel coated with Ti-W-N

Coatings of Ti-W-N on Si(100) and AISI D3 steel substrates have been deposited by an r.f. magnetron sputtering technique from a binary (50vol.% Ti, 50vol.% W) target. Their electrochemical characteristics have been studied by potentiodynamic and Electrochemical Impedance Spectroscopy (EIS) techniques and their mechanical properties were studied using depth-sensing nanoindentation. XRD was used to determine the phase composition, and a strong preferred orientation of the TiN(111), TiN(200), WN(107) and WN(220) planes was detected. Depth sensing nanoindentation measurements were used to investigate the elasto-plastic behavior of Ti-W-N coatings. Each group of samples was deposited under the same experimental conditions (power supply, Ar/N2 gas mixture and substrate temperature), except the d.c. negative bias voltages that varied (0 V, −50 V, −100 V) in order to study its effects on the mechanical and electrochemical properties of AISI D3 steel substrate with Ti-W-N coatings. The measurements showed that the hardness and elastic modulus increased from 19 GPa to 30 GPa and from 320 GPa to 390 GPa, respectively, as a function of the increasing negative bias voltages or bias current density. Coating indentation track and coating–substrate debonding have been observed with atomic force microscopy on the indentation sites (AFM-IS). Finally, the corrosion behavior obtained by Ti-W-N coatings was studied in relation to the increase of the bias voltage. The obtained results have shown that at the higher negative bias voltage or bias current density, the steel with Ti-W-N coatings presented the lowest corrosion resistance.