Plasma-Sprayed Ti6Al4V Alloy Composite Coatings Reinforced with In Situ Formed TiB-TiN
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Plasma-Sprayed Ti6Al4V Alloy Composite Coatings Reinforced with In Situ Formed TiB-TiN Akrity Anand1 • Mitun Das1 • Biswanath Kundu1 • Vamsi Krishna Balla1 Subhadip Bodhak1 • S. Gangadharan1
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Submitted: 8 August 2017 / in revised form: 22 September 2017 ASM International 2017
Abstract Plasma spraying was used to deposit premixed Ti6Al4V ? 15 wt.% BN powder on titanium substrate to fabricate Ti6Al4V matrix composite coatings reinforced with in situ synthesized TiB-TiN. The formation of in situ TiB-TiN reinforcements increased with plasma power. The in situ reaction appears to be complete under present experimental conditions but with considerable oxidation of Ti in the composite coatings. The hardness of composite coatings was 7 times higher (855HV), and the in vitro wear rate (2.4 9 10-5 mm3/N m) was one order of magnitude less than that of titanium substrate. However, the microstructural non-uniformity decreased the corrosion resistance of these composite coatings in Hank’s balanced salt solution. Keywords corrosion in situ reinforcement plasma spraying titanium boride titanium nitride wear
Introduction The most popular metallic biomaterials namely pure titanium (Ti) and its alloys are well known for their biocompatibility, corrosion resistance and high specific strength (Ref 1). However, their application is restricted to nonarticulating implants, such as fracture plates, screws, hip stem, due to poor wear resistance of these materials (Ref 1, 2). The poor wear resistance of articulating biomaterials
& Vamsi Krishna Balla [email protected]; [email protected] 1
Bioceramics and Coating Division, CSIR-Central Glass and Ceramic Research Institute (CGCRI), 196, Raja S.C. Mullick Road, Kolkata 700 032, India
invariably generates large amount of particulate wear debris that leads to osteolysis followed by aseptic loosening of the implants (Ref 3). As a result, the demand for development of wear-resistant coatings on Ti and its alloys, to improve their tribological properties for wear-resistant implant applications, is continuously increasing. In the past, several researchers have attempted to create hard and wear-resistant surfaces on Ti and its alloys using physical vapor deposition, chemical vapor deposition, ion implantation, etc. (Ref 4-7). However, in vivo efficacy of these coatings has been very poor due to interfacial delamination, shallow penetration depth, thin coating and inherent brittleness (Ref 8). On the other hand, laser deposition has been widely used to fabricate thick titanium matrix composite (TMC) coatings with good interfacial bonding with the substrate. Strong interfacial bonding of these laserprocessed coatings has been attributed to the complete melting of the metal/alloy powders and substrate surface when high-power focused laser beam was used (Ref 9). Laser-deposited Ti6Al4V alloy composite coatings reinforced with TiN was found to exhibit high hardness of 1138 ± 61 HV, and under identical test conditions their wear resistance (3.74 9 10-6 mm3/N m) has b
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