a b s t r a c tThe effect of laser shock peening on the high temperature oxidation resistance of commercial pure titanium at high temperature (700°C) was studied in long-time (3000 h) exposure under dry air. A reduction of the gain mass by a factor 4 was found for laser-shock peened (LSP) samples compared to untreated titanium, which supports the interest of laser-shock treatment for the improvement of high temperature resistance. Short-durations (10 h and 100 h) oxidation experiments, devoted to investigate the influence of the LSP treatment on the first stages of the oxidation process, were also carried out by TGA. Several techniques as scanning electron microscopy, hardness and roughness measurements, X-ray diffraction and X-ray photoelectron spectrometry, microRaman spectroscopy, nuclear reaction analysis and electron backscattered diffraction were used to characterize the sample after laser treatment and oxidations. The formation of a continuous nitrogen-rich layer between the oxide layer and the α-case area in LSP samples appears to be the key factor to explain the reduction of oxygen diffusion, and thus the improvement of the oxidation resistance of laser shocked titanium. Moreover, the graintexture of LSP samples after oxidation can also explain the improvement of the high temperature oxidation resistance after long times exposures.

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International audienceThe excellent combination of light-weight and good mechanical propertiesmakes titanium alloys attractive for compressor section components in gasturbine engines (temperature between 250 and 600 C). However, above 600 C,the formation of an unprotective oxide layer facilitates the oxygen diffusion into thealloy. In this experimental study, pure titanium was treated with mechanical surfacetreatment to promote better protection against oxidation at high temperature. Shotpeenedand laser-shock peened specimens were compared to untreated samples interms of oxidation behavior at high temperature. We used thermal gravimetricanalysis to oxidize the samples at 700 C for 100 h. Subsequently, XRD, opticalmicroscopy, SEM/EDS, NRA, micro-Raman spectroscopy, and micro-hardnesswere used to characterize the oxide scale and the alpha-case layer formed during thehigh-temperature exposure. The shot-peened samples oxidized less (-45%) than theuntreated and laser-shock peened samples. This behavior was attributed to theformation of a continuous nitride layer between oxide and meta