Influence of Mechanical Surface Treatment on High-Temperature Oxidation of Pure Titanium

Abstract

The excellent combination of light-weight and good mechanical properties makes titanium alloys attractive for compressor section components in gas turbine engines (temperature between 250 and 600 °C). However, above 600 °C, the formation of an unprotective oxide layer facilitates the oxygen diffusion into the alloy. In this experimental study, pure titanium was treated with mechanical surface treatment to promote better protection against oxidation at high temperature. Shot-peened and laser-shock peened specimens were compared to untreated samples in terms of oxidation behavior at high temperature. We used thermal gravimetric analysis to oxidize the samples at 700 °C for 100 h. Subsequently, XRD, optical microscopy, SEM/EDS, NRA, micro-Raman spectroscopy, and micro-hardness were used to characterize the oxide scale and the alpha-case layer formed during the high-temperature exposure. The shot-peened samples oxidized less (−45%) than the untreated and laser-shock peened samples. This behavior was attributed to the formation of a continuous nitride layer between oxide and metal.