title: In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.
abstract: Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants.
authors.affiliation: Bioceramics and Coating Division, CSIR-Central Glass & Ceramic Research Institute, 196 Raja S. C. Mullick Road, Kolkata-700032, India; Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai-60036, India.
authors.forename: Mitun
authors.initials: M
authors.lastname: Das
authors.forename: Kaushik
authors.initials: K
authors.lastname: Bhattacharya
authors.forename: Stanley A
authors.initials: SA
authors.lastname: Dittrick
authors.forename: Chitra
authors.initials: C
authors.lastname: Mandal
authors.forename: Vamsi Krishna
authors.initials: VK
authors.lastname: Balla
authors.forename: T S
authors.initials: TS
authors.lastname: Sampath Kumar
authors.forename: Amit
authors.initials: A
authors.lastname: Bandyopadhyay
authors.forename: Indranil
authors.initials: I
authors.lastname: Manna
mesh_terms: D000497:Alloys / Q000737:chemistry*; D001672:Biocompatible Materials / Q000737:chemistry* / Q000494:pharmacology; D001896:Boron Compounds / Q000737:chemistry*; D002460:Cell Line; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; D001896:Boron Compounds; C079804:titanium boride; C031462:titanium alloy (TiAl6V4); C041500:titanium nitride; D014025:Titanium
keywords: Laser processing; Load-bearing implants; Titanium boride; Titanium nitride; Wear