Cavitation Resistance of TiN Nanocrystalline Coatings with Various Thickness
TiN nanocrystalline coatings of various thicknesses deposited on austenitic stainless steel, X6CrNiTi18-10, by means of the cathodic arc evaporation method were investigated in a cavitation tunnel with a slot cavitator. The estimated cavitation resistance parameters of the coatings were the incubation period and total mass loss. It was found that the incubation periods of the 4 μm and 7.8 μm-thick TiN coatings were over two and half times longer than that of the uncoated X6CrNiTi 18-10 steel and the total mass losses of these coatings were approximately half lower than of the uncoated specimen. The scanning electron microscope analysis indicated that the damage process of the TiN-4 coating originates from the micro-folding and coating fracture arises on the top of the micro-folds, whiles the TiN-8 and TiN-12 coatings were removed in the form of thin flakes. The factors mainly responsible for cavitation resistance of the TiN coatings are ability to plastic deformation of the coating and coating adhesion.
Rafał Chodun, Katarzyna Nowakowska-Langier and Krzysztof Zdunek
This paper presents the effects of elimination of current oscillations within the coaxial plasma accelerator during IPD deposition process on the morphology, phase structure and properties of synthesized TiN coatings. Current observations of waveforms have been made by use of an oscilloscope. As a test material for experiments, titanium nitride TiN coatings synthesized on silicon and high-speed steel substrates were used. The coatings morphology, phase composition and wear resistance properties were determined. The character of current waveforms in the plasma accelerator electric circuit plays a crucial role during the coatings synthesis process. Elimination of the current oscillations leads to obtaining an ultrafine grained structure of titanium nitride coatings and to disappearance of the tendency to structure columnarization. The coatings obtained during processes of a non-oscillating character are distinguished by better wear-resistance properties.
The experimental resistance parameter for TiN coating to cavitation action
A series of cavitation erosion tests were carried out to investigate the resistance of the TiN coatings to cavitation action. The TiN coatings were deposited at various deposition parameters on austenitic stainless steel, X6CrNiTi18-10, and with various thickness by means of the cathodic arc evaporation method (ARC PVD). Investigations were performed in a cavitation tunnel with a slot cavitator. The investigations show that hardness, Young's modulus, adhesion and coating thickness have an influence on coating endurance to cavitation degradation. The obtained parameter H•LC2/E•h1/2 shows very good fitting to date points (R2=0.96). With the increase of the H•LC2/E•h1/2 parameter the mass loss decreases indicating a continuous improvement in the cavitation erosion resistance.