Jagadeeshanayaka, N.Kele, S.N.Jambagi, S.C.2026-02-042023Langmuir, 2023, 39, 48, pp. 17513-175287437463https://doi.org/10.1021/acs.langmuir.3c02840https://idr.nitk.ac.in/handle/123456789/21550Due to its resemblance to the bone, hydroxyapatite (HA) has been widely used for bioactive surface modification of orthopedic implants. However, it undergoes significant thermal decomposition and phase transformations at a high operating temperature, leading to premature implant failure. This investigation uses high-velocity air-fuel (HVAF) spray, an emerging low-temperature thermal spray technique, to deposit HA over the Ti-6Al-4V substrate. Coating characteristics, such as the crystallinity index and phase analysis, were measured using X-ray diffraction, Raman analysis, and Fourier transform infrared spectroscopy, residual stress using the sin2ψ method, and tribological performance by a fretting wear test. The coating retained an over 90% crystallinity index, a crystallite size of 41.04 nm, a compressive residual stress of −229 ± 34.5 MPa, and a wear rate of 1.532 × 10-3 mm3 N-1 m-1. Computational in-flight particle traits of HA particles (5 to 60 μm) were analyzed using computational fluid dynamics; it showed that 90% of particles were deposited at a 700 to 1000 m/s velocity and a 900 to 1450 K temperature with a 2.1 ms mean residence time. In-flight particle oxidation was minimized, and particle impact deformation was maximized, which caused severe plastic deformation, forming crystalline, compressive residual stressed coatings. The thermal decomposition model of low-temperature HVAF-sprayed HA particles helped to understand the implants’ crystallinity index, residual stress, and tribological characteristics. Hence, this experimental and computational analysis shows that the HVAF process can be a promising candidate for biomedical applications for having strong and durable implants. © 2023 American Chemical Society.AirAluminum alloysComputational fluid dynamicsCrystallinityDuctile fractureFourier transform infrared spectroscopyMedical applicationsParticle size analysisResidual stressesStrain rateTemperatureTernary alloysThermolysisTitanium alloysTribologyWear of materialsBioactive surfacesCrystallinity indexHigh velocity air fuelsHydroxyapatite implantsHydroxyapatite particlesIn-flight particlesLows-temperaturesParticle behaviorPowder particlesSurface-modificationHydroxyapatitefuelhydroxyapatiteplasticaerosolairarticlecomputational fluid dynamicscontrolled studydecompositionflightlow temperaturemean residence timeoxidationphysiological stresspowdertemperaturevelocityX ray diffraction