Room temperature deposition of (Ti,Al)N and (Ti,Al)(C,N) coatings by pulsed laser deposition for tribological applications

Titanium–aluminium based nitride (Ti,Al)N and carbonitride (Ti,Al)(C,N) hard coating systems possess excellent tribological behaviour in metal cutting and polymer forming contacts. In the present work (Ti,Al)N and (Ti,Al)(C,N) coatings were deposited by employing the pulsed laser deposition (PLD) technique. A pulsed Nd:YAG laser with 1064 nm wavelength was used for the vaporization of TiAl targets in low-pressure N2 or N2/C2H2, atmospheres at room temperature. The highly ionized metal vapour was deposited onto polished substrates (molybdenum, AISI D2). The coatings were characterized by light-microscopy, scanning electron microscopy, X-ray diffraction and hardness tests. The variation of the deposition parameters causes a change of the chemical composition, the texture and crystallinity of the coatings and, consequently, the mechanical properties and tribological behaviour. The latter was characterized in pin-on-disc tests at room temperature by using coated discs and uncoated AISI 52100 (DIN 100Cr6) steel and alumina pins as counterparts. The results demonstrate the excellent industrial applicability of these coatings for cold-forming operations: very low-wear rates were found for the (Ti,Al)N coatings. In contrast, the (Ti,Al)(C,N) coatings possess low-friction coefficients of approximately 0.2. As an outstanding advantage of these coatings, which were deposited at the room temperature by the PLD process, their excellent adhesion to the substrate can be pointed out, reaching the highest level (HF 1) in the Rockwell indentation test.