Three different coatings (TiN, CrN and AlCrN layers) were deposited on an AISI 52000 steel substrate with the physical vapour deposition technique. Adhesion of the coatings was investigated by microindentation, scratch testing and cyclic impact testing. In the microindentation tests, circumferential cracks were observed around the indentations on each coating. The scratch tests revealed the critical forces that accompanied the various types of degradation imposed by scratching. The TiN coating demonstrated the lowest critical force of adhesion, whereas the CrN coating had the highest and AlCrN had an intermediate critical force of adhesion. According to the results from impact testing, all coatings displayed circumferential and radial cracks that degenerated in varying manners during the cycles. Indeed, the cyclic impact introduced crazing on the TiN coating as a broad halo around the imprint, while for AlCrN, an intensive delamination was observed. The CrN coating was found to crack, but did not delaminate.

The aim of this work was to investigate the nanomechanical, adhesion and corrosion resistance of hydroxyapatite (HAP) coatings. The electrodeposition process was used to elaborate the HAP coatings on Ti6Al4V alloy. The effect of hydrogen peroxide concentration H2O2 on the electrolyte and the heat treatment was studied. Surface morphology of HAP coatings was assessed, before and after heat treatment, by scanning electron microscopy associated with X-ray microanalysis (SEM-EDXS). Moreover, X-ray diffraction (XRD) was performed to identify the coatings’ phases and composition. Nanoindentation and scratch tests were performed for nanomechanical and adhesion behavior analysis. The corrosion resistance of the uncoated, the as-deposited, and the heat-treated coatings was investigated by electrochemical test. The obtained results revealed that, with 9% of H2O2 and after heat treatment, the HAP film exhibited a compact and homogeneous microstructure. The film also showed a crystal growth: stoichiometric hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP). After heat treatment, the nanomechanical properties (H, E) were increased from 117 ± 7 MPa and 24 ± 1 GPa to 171 ± 10 MPa and 38 ± 1.5 GPa respectively. Critical loads (LC1, LC2, and LC3) were increased from 0.78 ± 0.04, 1.6 ± 0.01, and 4 ± 0.23 N to 1.45 ± 0.08, 2.46 ± 0.14, and 4.35 ± 0.25 N (respectively). Furthermore, the adhesion strength increased from 8 to 13 MPa after heat treatment. The HAP heat-treated samples showed higher corrosion resistance (Rp = 65.85 kΩ/cm2; Icorr = 0.63 µA/cm2; Ecorr = −167 mV/ECS) compared to as-deposited and uncoated samples.

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