HARD COATINGS ON MAGNESIUM ALLOYS BY SPUTTER-DEPOSITION USING A PULSED DC BIAS VOLTAGE

An increasing use of magnesium-based light-metal alloys for various in dustrial applications was predicted in different technological studies . Companies in different branches have developed machine parts made of magnesium alloys (e.g. cars, car engines, sewing and knitting machine s). Hence, this work was started to evaluate the ability of hard coati ngs obtained by physical vapour deposition (PVD) in combination with c oatings obtained by electrochemical deposition to protect magnesium al loys against wear and corrosion. TiN hard coatings were deposited onto magnesium alloys by unbalanced magnetron sputter deposition. A bipola r pulsed d.c. bias voltage was used to limit substrate temperatures to 180 degrees C during deposition without considerable loss of microhar dness and adhesion. Adhesion, hardness and load-carrying capacity of T iN coatings deposited directly onto magnesium alloys are compared with the corresponding values of TiN coatings deposited onto substrates wh ich had been coated electroless with an Ni-P alloy interlayer prior to the PVD.