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Abstract
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This paper evaluates the corrosion resistance of a duplex treated AISI H11 tool steel. The duplex treatment is composed of hot wall plasma nitriding, in order to surface harden the sample, followed by TiN nanostructure coating, using plasma assisted chemical vapor deposition (PACVD). Plasma nitriding was carried out in a gas mixture of 25 vol.% N2, 75 vol.% H2 at 500˚C for 4 h. PACVD treatment was performed in the same chamber in an atmosphere containing Ar, N2 and H2 gases along with TiCl4 vapor, for 4 h, at a chamber pressure of 3 mbar, for different process temperatures of 470, 490, and 520 ˚C. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and RAMAN spectroscopy as well as potentiodynamic polarization test in 3.5% NaCl solution were used to study the treated surfaces. Results indicate that the corrosion resistance of the samples with TiN coatings, increased about 10 times in comparison to the untreated samples. Furthermore, increasing PACVD treatment temperature from 450 to 520˚C, increases the corrosion resistance of the coated samples.
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