Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom Mechanical and tribological properties evaluation of plasma-sprayed shape memory alloy coating B. Swain a , P. Mallick a,b , Ram K. Gupta c , S.S. Mohapatra d , G. Yasin e , T.A. Nguyen f , Ajit Behera a, ⁎ a Department of Metallurgical and Materials Engineering, National Institute of Technology, Rourkela, India b Thermal Spray Division, Hindustan Aeronautics Limited, Koraput, India c Department of Chemistry, Pittsburg State University, Pittsburg 66762, KS, USA d Department of Chemical Engineering, National Institute of Technology, Rourkela, India e Institute for Advanced Study, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, Guangdong, China f Institute for Tropical Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam article info Article history: Received 14 December 2020 Received in revised form 30 December 2020 Accepted 31 December 2020 Available online 12 January 2021 Keywords: Plasma spray Coating NITINOL Stand-off distance Failure analysis Erosion abstract In the current investigation, an elemental blending of equiatomic Ni and Ti powder was considered to spray on mild steel by the atmospheric plasma spray process. The results revealed that the coating developed with 120 mm stand-off distance (SOD) has better mechanical properties such as microhardness and ad- hesion strength. Again, SOD predominantly infuences the formation of intermetallics (NiTi, Ni 3 Ti, Ti 2 Ni, and TiO) that helps to enhance the microhardness (683.85 HV) as well as the mechanical interlocking and chemical bonding that is solely responsible for the high adhesion strength (43.17 MPa) of the coating. The failure analysis of the coating developed at too high and too low SOD revealed that rapid expansion of gas stream, reduction in enthalpy of particles, improper heat transfer, burning of splat, agglomeration of par- ticles during fight, and oxidation are the key factors responsible for the reduction in mechanical properties of plasma-sprayed Ni-Ti alloy (NITINOL) coatings. In addition to the above, the solid particle erosion analysis revealed the increase in brittleness of the coating with increasing in SOD. The surface morphologies of the eroded surface depict various erosion mechanisms at both 45° and 90° impingement angles such as chip formation, lip formation, plastic deformation, scratches, etc. © 2021 Elsevier B.V. All rights reserved. 1. Introduction Solid particle erosion is a surface degradation phenomenon that generally occurred in a dusty environment. It decreases the surface durability, increases maintenance cost, and decreases the overall productivity of industries such as steam, jet and gas turbines, pi- pelines, fuidized bed combustion systems, etc [1]. Therefore, various materials have been coated on the substrate surfaces to protect the surface from erosion [2–4]. In the emerging era of material, the re- searchers have introduced a new kind of advanced material, known as a smart material. Among all the smart materials, Ni-Ti alloy (NI- TINOL) has two extraordinary properties, which are shape memory effect and pseudoelasticity [5]. NITINOL was discovered by Buehler and his co-workers in 1963 at U.S Naval Ordinance Laboratory (NOL) [6]. In addition to the above magical properties, NITINOL has other inherent properties such as strength at fatigue load [7], high damping behavior [8,9], high resistance to corrosion and wear [10–12], water erosion resistance [13], and hardness at high tem- perature [14]. Due to the above-mentioned properties, NITINOL has a broad area of applications, such as naval industries, aerospace in- dustries [15], civil constructions [16], biomedical device industries [17], etc. However, NITINOL is very expensive for bulk applications. Therefore, researchers often develop a coating of NITINOL on a substrate of different materials to extract all the inherent properties of the smart alloy in an economical way. It has been reported in the literature regarding different coating methods to deposit NITINOL on various substrates. Ho et al. deposited NITINOL on a heated target by sputter deposition method and revealed the dependency of prop- erties on the temperature of the target [18]. Moreover, Behera et al. developed a thin flm of NITINOL on a heated substrate by magne- tron sputtering technique and obtained a good quality of the flm which exhibits a transformation path B2→B19′ [19]. In the follow-up research, Scheitler et al. fabricated a NiTi coating on Ti sheet metal using a laser metal deposition technique and investigated the https://doi.org/10.1016/j.jallcom.2021.158599 0925-8388/© 2021 Elsevier B.V. All rights reserved. ]] ]] ]]]]]] ⁎ Correspondence to: Advanced Materials Processing and Research laboratory (AMPRE-Lab), Department of Metallurgical and Materials Engineering, NIT Rourkela, 769008, India. E-mail address: ajit.behera88@gmail.com (A. Behera). Journal of Alloys and Compounds 863 (2021) 158599