CRACK RESISTANCE OF PVD COATINGS: INFLUENCE OF SURFACE TREATMENT PRIOR TO DEPOSITION

摘要

The crack resistance of three different PVD coatings, TiN, Ti (C,N), and a multilayer system of alternating TiN and TiAlN, have been investigated. The three coating systems were deposited onto substrates with a different surface roughness to study the influence of this pretreatment on the crack resistance of the coatings. First, the microstructure and state of stress of the three PVD systems were determined using X-ray diffraction and scanning electron microscopy. Then the coatings are loaded in tension in an ESEM to carry out in situ bending experiments, to assess the crack resistance of the layers. Studying the results of the bending experiments in relation to the characteristic properties of the coatings shows that the compressive residual stresses have a large influence on the moment the first cracks arise. After the initiation of the first crack, the crack resistance of TiN, deposited on the smoothest substrate, is much better than that of TiN/TiAlN and Ti(C,N). Increasing the interface roughness for the Ti(C,N) and the TiN/TiAlN results in an increased crack resistance. For the coatings deposited on the roughest substrates, the crack resistance is, approximately, the same for the three different systems. Spallation of the coatings also has been observed but does not occur frequently.