Tribological behaviour of Ti-Al-B-N-based PVD coatings

PVD-coatings based on TiB2 are expected to show high wear resistance and low tendency of adhesion on metal forming tools. Coating adhesion and morphology can be modified over a wide range by varying the content of nitrogen (N-2) and the deposition parameters power and bias voltage. All coatings were deposited using commercial unbalanced magnetron equipment, the deposition was homogeneous in a volume of 400 x 400 x 400 mm(3). Hipped and hot pressed TiB2-targets were used, nitrogen (N-2) was added as gas, Ti and Al by a solid Ti-Al-target. The tribological behaviour was tested by a pin-on-disc wear test. The coatings investigated were TiB2, TiAlB(N), TiAl(N) and TiB2/TiAl(N). As counterpart in the pin-on-disc wear test, 6 mm diameter spheres of steel (100Cr6), aluminium, brass and bronze were used. The experiments showed a non-uniform wear behaviour. For the combinations TiAlB(N) and TiB2 versus aluminium, a low wear volume of the coating and adhesive tendency was found. Brass led to abrasive wear on all coatings, whereas bronze showed a strong adhesive tendency on all tested coatings. Using a steel sphere the dominant wear mechanism was tribochemical oxidation.