Investigation of Tribological Behavior of Plasma Sprayed NiTi Coating for Aerospace Application

Abstract

In the absence of any literature regarding the development of erosion resistance protective coatings on the aerospace engine parts using NiTi alloy, the current work has been focused on the detail investigation of the solid particle erosion resistance of the NiTi coating developed by atmospheric plasma spray technique. The coating has been prepared by considering an elemental mixture of equiatomic Ni and Ti powder as feedstock material with different plasma arc currents and primary gas flow rates. The quality of the coatings has been checked by different characterization techniques like x-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy. The defects observed from the microstructural investigation sometimes lead to more erosion and sometimes resulted in less erosion rate. The investigation of the effect of the porosity percentage on the erosion rate revealed that as the porosity percentage increases, the erosion rate increases at both 45 degrees and 90 degrees erodent impingement angles due to the lack in strength at the edges of the pores. Furthermore, the surface area of the roughness peaks, the stress concentration at the gap between the roughness peaks and height of the surface profile are mainly responsible for the erosion performance at both the erodent impact angles. The erosion rate is inversely proportional to the microhardness of the coatings. In addition to the above, according to the results disclosed by the erosion performance at different impingement angles, the coating is brittle in nature. The surface morphological study of the eroded coatings indicated various erosion mechanisms like plastic deformation, plowing, microcutting, lip formation, scratches, groove formation on the coatings impinged at 45 degrees impact angle and groove formation, splat fracture, splat fragmentation, splat delamination, pit formation on the coatings impinged at 90 degrees impingement angle.