Structural, mechanical and tribological investigations of pulsed laser deposited titanium nitride coatings

The high hardness and the low-wear rates characterize the outstanding tribological behaviour of titanium nitride (TiN) making it to the most widespread material for hard coatings, which were deposited industrially in recent years by employing various deposition methods. For coating of heat sensitive materials and machine parts at low temperatures down to room temperature, only a few deposition techniques can be applied. One of these is the pulsed laser deposition (PLD) method. In this work a multi-spot PLD system with four Nd:YAG laser beams (1064-nm wavelength) was applied to vaporize titanium targets in low-pressure N 2 atmospheres at room temperature. For the deposition of the TiN coatings, high speed tool steel (AISI M2) and corrosion resistant steel (AISI 630 HT) substrates were used. To investigate the differences of film growth in dependency of the target–substrate arrangement, the substrate surfaces were situated parallel (on-axis) and rectangular (off-axis) to the target. The coatings were examined by light-microscopy, scanning electron microscopy, X-ray diffraction, nanoindentation and pin-on-disc tests against ball-bearing steel (DIN 100Cr6/AISI 52100) and alumina (Al 2 O 3 ) counterparts. The results indicate a high influence of the target–substrate arrangement on the textures, residual stresses and hardnesses of the TiN coatings. In spite of these differences all coatings on both on-axis and off-axis placed substrates possess excellent adhesion and high-wear resistance.