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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.

Nano-multilayer PVD thin films were deposited on 100C6 (AISI 52100) steel substrate by a PVD magnetron sputtering system. The morphological and microstructural properties were evaluated by using atomic force microscopy and scanning electron microscopy. Residual stresses in all coatings were determined by XRD using the sin2w method. Microindentation and scratch tests were performed, respectively, with a Vickers hardness testing machine and scratch test. These tests were carried out on several coatings with various structures, and compositions TiN single layer, TiAlN multilayer, and TiN/TiAlN nano-multilayer. Hardness measurements were performed by using Vickers imprint using the Jonsson and Hogmark model. Critical loads were measured by scratch test. The results show that the coatings topography was dominated by domes and craters which were uniformly distributed over the surface, and all coatings showed a columnar structure. Damage mechanisms under microindentation and scratch depended on coatings structure and composition. Mechanical and structural properties control the damage behavior and the adhesion quality of coatings. The multilayer structure provides an increase in residual stress, hardness, and failure resistance and a decrease in cracks propagation and adhesion resistance.

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