Optimization of in situ substrate surface treatment in a cathodic arc plasma: A study by TEM and plasma diagnostics

Cr ions generated by a steered cathodic arc discharge are utilized to control and enhance the adhesion properties of 3.5 mum thick TixAl(1-x)N based coatings deposited on high speed steel substrates, A two-step etching procedure (negative substrate bias, U-S=1200 V) is suggested, operating the arc discharge initially in an Ar atmosphere (p(Ar)=0.09 Pa.. 6.75x10(-4) Torr) to achieve predominantly metal removing effects (etching rate: 9 nm min(-1)) with a mixture of Ar and Cr ions. In the second stage at residual gas pressure level (p(Ar) less than or equal to 0.006 Pa, 4.5x10(-5) Torr, etching rate: 4 nm min(-1)) pure Cr ion irradiation leads to a Cr penetration as deep as 20 nm with a Cr accumulation of approximately 37 at % at the interface substrate/coating. This procedure promotes localized epitaxial growth of TixAl(1-x)N and enhances critical load values up to 85 +/-5 N. (C) 2001 American Vacuum Society.