Microstructural and electrochemical characterization of Ti Films deposited on steel substrates by magnetron sputtering

摘要

Various techniques have been used to coat metal substrates with noble metals in order to produce corrosion-resistant materials. This paper studies the quality of titanium films deposited on AISI 4340 steel substrates by magnetron sputtering, and their corresponding corrosion behaviour. Coated specimens were characterized using microstrutural and electrochemical techniques. SEM analysis revealed that a film of columnar structure and high density was obtained when the substrate voltage and temperature were -300V and 500 deg C, respectively. For those parameters, the electrochemical potentiodynamic tests showed an improvement in the corrosion resistance of Ti-coated substrates as compared to unprotected AISI 4340 steel. For Ti-coated specimens typical current densities in range of 6 X 10~(-7) A/cm~2 and 6.3X10~(-6) A/cm~2 were measured at the potential range of 0.17 to 1.5 V. As for uncoated steel, the values were considerably higher (0.1 A/cm~2) for the same potential range, suggesting a substantial improvement in the corrosion resistance of the material. In spite of this fact, the coated material was susceptible to localized corrosion in exposed areas of the substrate, mainly as a result of substrate topography and coating quality.