SURFACE MODIFICATION OF STEEL SHEETS USING DRY PROCESS

Using an arc-discharge ion plating, effects of pretreatments and plating conditions on performances of deposited films are investigated. Both preheating and argon ion bombardment were essential pretreatments before ion plating in order to improve adhesion and formability of ion-plated chromium films, because these pretreatments attribute to the sputter cleaning effect on the surface of the steels and the formation of the mixing zone of the deposited film and the substrate. Epitaxially grown platelike grains, which appeared in the ion-plated films pretreated by preheating and argon ion bombardment, were effective in improving the formability by coarsening their grains. Much greater formability of the chromium films and the titanium films was achieved compared to vacuum deposition. This is because ion-plated films initially grew uniformly on the substrates and the grain sizes were coarsened with the minus bias voltage increased. This resulted in the reduction of the grain boundaries, which could be the initiation sites and the propagation paths of the cracks. In addition, the low hardness of the ion-plated films resulted in the easy deformation and hence excellent formability.