**Abstract**

A MWCNT-induced hydroxyapatite, air plasma spray coatings were produced on SS-316 L, CoCrMo, and Ti6Al4V alloys at varied weight percent ratios. The shape, thickness, adhesion, structure, and content of the APS-treated samples, as well as particle distribution, were studied using an X-ray diffraction, scanning electron microscope, Fourier transform infrared, and 3D-profilometer. The study looks at dry and wet unidirectional sliding wear behaviors, as well as the influence of incorporating carbon nanotubes in different weight percent to hydroxyapatite by plasma spraying on its tribological properties in physiological condition. In-vitro investigation was conducted in controlled environment to model complicated interactions among cells growth factors. Both CNT and HA particles were absorbed into the APS layers, as evidenced by the results. Crystallinity and volume percent with open porosity were substantially higher in the APS-CNT imposed HA coating than in the control. When compared to pure HA coating, the enhanced hardness ranged from 2.4 to 5.6 GPa, the modulus of elasticity ranged from 105 to 172 GPa, and the fracture toughness from 0.6 to 2.4 MPa.m1/2, with a reduced wear rate of 50.2 × 10−5 mm3 to 4.2 × 10−5 mm3 N−1 m−1. CNT addition has no negative effect on osteoblast proliferation and cell viability.

**Keywords:** hydroxyapatite, carbon nanotube, air plasma spraying, biocoating, tribology, biocompatibility
