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MRS Advances © 2020 Materials Research Society DOI: 10.1557/adv.2020.158

Effects of niobium (Nb) on mechanical properties of laser coated Nitinol (NiTi) used for surface modification of Ti6Al4V alloy B.S Skhosane1*, M Tlotleng1, 2, and S.L Pityana1, 3 1Laser

Enabled Manufacturing National Laser Centre CSIR, Pretoria, 0001, South Africa of Mechanical Engineering Science, University of Johannesburg, Auckland Park Campus, Johannesburg, 2006, South Africa 3Department of Chemical and Metallurgical Engineering, Tshwane University of Technology, Pretoria, 0001, South Africa 2Department

Abstract:

Laser surface treatment is widely used as an engineering technique due to its special characteristics and several advantages over other surface modification techniques. In the present study, elemental mechanically pre-alloyed powder consisting of Niobium, Titanium and Nickel was deposited onto a grade 5 Titanium alloy substrates to form a high wear resistance coating. This was such that the surface mechanical properties of the base metal can be improved. The fabricated samples were characterised using optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Differential Scanning Calorimeter (DSC), micro hardness tester and wear machine. The deposited coatings were well bonded and consisted of various phases. Hardness was seen decrease with increase in Nb content while wear resistance increasing with increase in niobium content. 1.

INTRODUCTION:

Titanium and titanium alloys are widely used in manufacturing aerospace components and chemical industries components due to their outstanding properties such as high specific strength ratio, excellent corrosion resistance and good creep resistance [1, 2]. However, their use in mechanically wear conditions is limited due to their poor wear resistance properties [1, 3]. These limitations can be overcome by surface modification using surface engineering techniques. Methods such as laser cladding, nitriding and thermal spraying are amongst others constitute

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surface coating techniques in engineering field. Laser cladding technique is a superior surface modification technique owing to its special characteristics such as achieving good metallurgical bonding between the surface coating and the parent material with minimum dilution when compared to techniques such as thermal plasma spraying and submerge arc cladding [2]. Laser cladding uses low heat input, resulting in less distortion and minimum heat affected zone [2, 4]. This technique is often use in the refurbishment of worn parts, protection of new parent material against corrosion and hard facing of material [5]. In this study, Nitinol was laser cladded onto titanium substrate. Nitinol (Nickel-titanium or NiTi) has remarkable properties such as super-elasticity, shape memo