Surface modification of β-phase Ti implant by hydroaxyapatite mixed electric discharge machining to enhance the corrosion resistance and in-vitro bioactivity

• Published in: Surface & coatings technology 2017-10, Vol.326, p.134-145
• Main Authors: Prakash, Chander, Uddin, M.S.
• Format: Article
• Language: English
• Subjects: Corrosion resistance; Electric discharge machining; Hydroxyapatite (HA); In-vitro; MG-63 cell; Nanoporous biomimetic surface; β-Phase Ti implant
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2017.07.040

The study presented an innovative method for surface modification of β-phase titanium alloy using hydroxyapatite mixed electric discharge machining (HAM-EDM). The process enables one to deposit in-situ a biomimetic nano-porous HA-containing layer while shaping the base titanium, hence modifying the surface properties of the original substrate. A series of the dedicated HAM-EDM on titanium alloys have been conducted. Surface integrity, topography, and elemental composition of the modified surface were investigated by FE-SEM, EDS, XRD, and indentation techniques, while in vitro cell study was performed to evaluate biocompatibility and cell attachment of the treated surface. The morphology characterization results revealed that a natural bone-like nano-porous surface topography has been imparted on the β-phae Ti implant surface using the HAM-EDM. The EDS and XRD examinations showed that the deposited layer comprised of Ti, Nb, Ta, Zr, O, Ca and P elements and formed biocompatible phases such as Ca3(PO4)2, CaZrO3, Nb8P5, CaO, TiP, Nb4O5, and TiO2, TiH on the β-Ti implant surface, which improved the bioactivity of the alloy and beneficial for the promotion of osseointegration. The results revealed that a 18–20μm thick recast layer containing biocompatible phases was generated, which has excellent metallurgical bonding with the base surface and offered mechanical interlocking to delamination. The HA deposited surface shows am improved hardness of 1275HV which is 3-fold higher than the untreated surfaces; predominantly owing to the deposition of hard oxides on the modified surface. The HA-deposited bioceramic layer presented an excellent and higher corrosion resistance as compared to EDMed and un-treated specimens in simulated body fluid. The in-vitro bioactivity results confirmed that the nano-porous HA-containing layer exhibited the superior bioactivity and promotes adhesion, growth, proliferation, and differentiation of human osteoblastic MG-63 cells. [Display omitted] •Biomimetic HA-containing layer was deposited by electric discharge machining process.•During machining, very thick oxide layer of microhardness 1275 HV was obtained.•The HA-deposited layer has excellent metallurgical bonding with substrate and offered good mechanical interlocking.•The HA-containing layer has highest corrosion protection efficiency.•The HA-coating improved the cells adhesion, proliferation, and differentiation.