TEM Analysis of Wear of Ti/TiN Multi-Layer Coating in Ball-on-Disc Test
The wear mechanisms of Ti/TiN eight layered coatings ( =250nm) were investigated with ball-on-disc test. The coatings were obtained by hybrid pulsed laser deposition (PLD) technique. The wear test was done using Al2O3 ball-on-disc test at 1N/2000 cycles. Thin foils for TEM observations were cut from wear track using a Quanta 200 3D FIB (Focus Ion Beam) equipped with an Omniprobe lift-up system. The microstructure investigations were performed with the TECNAI G2 SuperTWIN FEG (200kV) transmission electron microscope. At the start of the wear the load applied to Al2O3 ball resulted in pushing-in of the coating into substrate causing its grooving of the shape corresponding to the ball diameter. The lining of the crater required strong coating deformation, which was plastic within Ti and mostly brittle in TiN layers. The vertical cracks in TiN were indeed stopped at the TiN/Ti interfaces, but reopen in lying below TiN layers. In applied wear conditions the continuity of Ti layers prevails over cracking of the TiN layers and resulted in layer-by-layer wear of investigated multilayer coating.
J. Dusza, R. Danzer, R. Morrell and G.D. Quinn
Ł. Major and J. Morgiel, "TEM Analysis of Wear of Ti/TiN Multi-Layer Coating in Ball-on-Disc Test", Key Engineering Materials, Vol. 409, pp. 123-127, 2009