TiC coatings prepared by pulsed laser deposition and magnetron sputtering

Abstract

Tribological properties of TiC coatings grown by pulsed laser deposition (PLD) and magnetron sputtering were investigated. The PLD TiC coatings grown at room temperature were found to be much harder than the TiC coatings grown by magnetron sputtering under the given experimental conditions. The hardness of PLD coatings deposited at room temperature was as high as 44 GPa, in contrast to ~20 GPa of the magnetron sputtered ones. The coefficient of friction of the PLD films measured with a pin-on-disk type tribometer had a typical value of about 0.2 when using a 440C stainless steel pin. Scratch tests indicated that magnetron-sputtered TiC coatings adhered well to the stainless steel substrates. The relatively poor adhesion of the PLD coatings obtained from this scratch test was probably partly due to their high brittleness and the relatively weak adhesive bond. However, the adhesion of PLD coatings could be improved by raising the substrate temperature slightly to 300 °C or by in situ laser annealing. The former was also able to maintain their hardness at a relatively high level. The adhesion of magnetron-sputtered TiC coatings could be modified by inserting a metallic interlayer between the coating and stainless steel substrate. Mo interlayer had a detrimental effect on the adhesion caused probably by the poor stress bearing capability of the porous Mo film deposited at low temperature. However, the insertion of both Ti and Cr interlayers enhanced the adhesion of TiC by as much as 25%.