DLC films deposited by bipolar pulsed DC PACVD

For engineering applications, diamond-like carbon films (DLC) are the most suitable coatings, when high wear-resistance and low friction is needed. One problem is their very poor adhesion to steel substrates when no intermediate layer is supplied. The most common method for depositing DLC-films is a plasma activated chemical vapour deposition process with radio frequency (rf PACVD, 13.56 MHz), which is technically difficult and expensive to scale up to industrial dimensions. The FhG-IST is testing different methods for plasma excitation, e.g. DC plasmas or hollow cathode excitation. It is assumed that these methods are easier and cheaper to scale up. In this paper the deposition of DLC coatings by bipolar-pulsed direct current PACVD (bip DCPACVD) is presented. 100Cr6 steel was used as substate material. The experiments were carried out in a commercially available plasma nitriding plant. The adhesion was improved by an intermediate Si-C:H layer with tetramethylsilane (Si(CH3)4) as a pre curser. Methane (CH4) was used for depositing the DLC films. The properties thus obtained are comparable to DLC films by rf PACVD.