TEM OBSERVATIONS OF THE WEAR OF Ti/TiN MULTILAYER COATINGS AFTER BALL-ON-DISC TEST

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TEM OBSERVATIONS OF THE WEAR OF Ti/TiN MULTILAYER COATINGS AFTER BALL-ON-DISC TEST

Journal Title: Tribologia - Year 2009, Vol 225, Issue 3

Abstract

The wear mechanisms of single- layered TiN coatings as well as multilayered Ti/TiN coatings (Λ =250nm) were investigated with ball-on-disc test. The coatings were obtained by the hybrid pulsed laser deposition (PLD) technique. The wear test was done using Al2O3 ball-on-disc test at 0.25 and 1N after 10000 and 2000 cycles, respectively. Thin foils for TEM observations were cut from the wear track using 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. Observations exhibited that the deposited TiN single layered coating was characterized by strongly defected columnar microstructure and the presence of micro-cracks along grain boundaries. Early stages of the wear process, where test was performed under 0.25N, showed that the micro-cracks at grain boundaries were much more pronounced and new ones additionally appeared cutting individual grains. The wear track formation starts with the removal of small pieces of individual grains leaving a “broken tooth” like line. The higher load (1N) resulted in activation of side slips along the existing cracks causing steps at the surface and corresponding dent in the substrate. Under the same loading in the central part of wear track, the TiN coating was fractured to a few micron size pieces, which were half way pushed into the steel substrate. The HRTEM observations of coating confirmed that the cracks formed during deposition were located at the column of crystallites boundaries, while wear caused the formation of intercrystalline cracks along {111} planes as well. In the case of multilayer coatings under the applied load, ceramic (TiN) layers were cracked while metallic layers deformed plastically. The vertical cracks in TiN were indeed stopped at the TiN/Ti interfaces, but reopen in TiN layers lying below. 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.<br/><br/>

Authors and Affiliations

Łukasz Major, Jerzy Morgiel, Marcin Kot, Wiesław Rakowski

Keywords

TEMPERATURE OF THE TOP LEVEL SURFACE OF PARTS OF AGRICULTURAL SOIL TILLING MACHINERY. PART I – THE ANALYSED OBJECTS, OPERATING CONDITIONS AND CONTACT TEMPERATURE MEASUREMENTS

During operation of working parts of agricultural machinery for soil tilling, the friction and abrasive wear of their surfaces occur due to the interaction of soil particles. Those processes cause a temperature increase...

EP ID EP516669
DOI -
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