Surface Deformation Recovery by Thermal Annealing of Thermal Plasma Sprayed Shape Memory NiTi Alloys

Abstract

The shape memory effect is the most important attribute of shape memory alloys where material can recover to its initial shape after deformation by heating above its transformation temperature. In this article, the thermally induced recovery of well-defined microscopic deformation in a NiTi shape memory alloy was investigated. Surface deformation was performed by indenting the plasma sprayed NiTi shape memory alloy in a martensitic phase at room temperature using spherical indenters. In this article, a series of indentations, scratch lines and wear lines were made on the surface of two different NiTi shape memory alloys at the micrometre scale using two spherical indenters with different radii. Three-dimensional imaging of indentation topography using scanning confocal microscopy provided direct evidence of the thermally induced martensitic transformation of these plasma sprayed thick films allowing for partial recovery on the micro-scale. The partial recovery is achieved at various indentation depths and for different scratches and wear volumes.