Effect of laser shock peening on the high temperature oxidation resistance of titanium

The 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, micro-Raman 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 grain-texture of LSP samples after oxidation can also explain the improvement of the high temperature oxidation resistance after long times exposures

Enhancing the Structural Performance of Lightweight Metals by Shot Peening

Lightweight metals and metal alloys provide the opportunity to fulfill the exigent weight-saving requirements for structural components. Mechanical surface treatments, in particular, shot peening and other varieties of impact-based surface treatments are found to be able to significantly promote the structural application of lightweight metals through enhancing their mechanical performance. Moreover, these treatments have substantiated a notable prospect to modulate the surface–environment interaction of the treated material, bringing in original functionalities in multiple fields of application. Herein, the current state-of-the-art in the implementation of shot peening-based surface treatments is reviewed regarding lightweight metallic materials. The recent advancements are described focusing on the foremost characteristics of the major lightweight metals commonly used in aerospace, automotive, and biomedical sectors. Emergent applications and the existing challenges are highlighted. Lastly, future perspectives on tailoring the effects of shot peening-based mechanical surface treatments to boost the appeal of lightweight metals as structural components are provided

High Temperature Oxidation Kinetics of Shot-Peened and Laser-Shock Peened Ti-Beta-21S

Isothermal oxidation tests of mechanically treated Ti-Beta-21S (TIMET, Ti-15Mo-3Nb-3Al-2Si, ASTM Grade 21) were performed under dry air at 650, 700 and 750 °C for 100 h and compared to untreated samples. Two different mechanical surface treatments were used: ultrasonic shot-peening (SP) and laser-shock peening (LSP). The study investigates the effect of both treatments on the oxidation kinetics of the process and the role of atmospheric nitrogen insertion. With this aim, oxidation experiments were also performed under pure oxygen. The results show that the oxidation is governed by diffusion after a short transient time. Both SP and LSP treatments improve the high temperature oxidation resistance of Ti-Beta-21S in dry air, but not in pure oxygen. The formation of a nitrogen-enriched layer at the oxidemetal interface, which is promoted by the mechanical surface treatments, explains the increase in the oxidation resistance in air by slowing down the diffusion of oxygen into the metal

Characterization of Oxygen-Enriched Layers of TA6V, Titanium, and Zirconium by Scanning Microwave Microscopy

International audienceA technique based on scanning microwave microscopy (SMM) has recently been developed to analyze solid solutions of light elements. This technique consists in local measurements of effects produced by electrical conductivity variations produced by light elements solutions in metals. The penetration of the microwaves into the metals depends on their frequency and the material parameters. Information regarding the local conductivity of the material at different depths can be recorded using various frequencies. In this paper, SMM measurements of the oxygen-enriched zone are presented for several materials: TA6V, pure Ti, and pure Zr. Comparisons with concentration measurements made by nuclear reaction analysis allow one to affirm that for all the materials investigated here the phase shift measured by SMM is proportional to the oxygen concentration dissolved into the metal. Calibration functions are proposed for each material and frequency used. After calibration, the SMM can be used to measure local enrichments

Effect of mechanical surface treatments on the high temperature oxidation of pure titanium: the role of nitrogen

The mechanically treated high temperature (700°C) oxidation of commercially pure titanium was studied for long exposures (3000 h). The treatments studied here are the shot-peening and the laser-shock peening. The mass gain was measured by discontinued weighing. SEM and Raman imaging revealed strong differences between laser-shock peened, shot-peened and untreated oxidized samples. The laser treatment leads to thin compact and protective oxide layer while the shot-peened and untreated samples exhibit cracked oxide layers. The distribution of light elements like carbon, oxygen and nitrogen was revealed by Ion Beam Analysis. The presence of nitrogen located at the interface between the oxide scale and the metal was revealed on laser-shock peened samples. It is supposed the nitrogen slows-down the oxygen diffusion into the metal. The extent of the oxygen-enriched metal is also smaller on LSP samples, which improves the ductility of titanium

TGF-beta1 in breast cancer-estrogen regulation

TGF-beta1 is a pluripotent cytokine with diverse effects in the normal development of mammary glands, and in the development of malignant tumors of the breast. The aim of the study was to determine the levels of TGF-beta1 in the group of advanced breast cancer, in which increased TGF-beta1 levels were most likely to be expected. TGF-beta1 levels were also compared with estradiol levels. Our results suggested that TGF-beta1 synthesis may be regulated by estrogen or anti-estrogen through ER. Finding of increased TGF-beta1 levels, due to its possible role in predicting invasive phenotype in later phases of tumor progression, may indicate the tendency of tumor tissue towards autonomy

Effect of mechanical surface treatments on the high temperature oxidation of pure titanium: the role of nitrogen

International audienceThe mechanically treated high temperature (700°C) oxidation of commercially pure titanium was studied for long exposures (3000 h). The treatments studied here are the shot-peening and the laser-shock peening. The mass gain was measured by discontinued weighing. SEM and Raman imaging revealed strong differences between laser-shock peened, shot-peened and untreated oxidized samples. The laser treatment leads to thin compact and protective oxide layer while the shot-peened and untreated samples exhibit cracked oxide layers. The distribution of light elements like carbon, oxygen and nitrogen was revealed by Ion Beam Analysis. The presence of nitrogen located at the interface between the oxide scale and the metal was revealed on laser-shock peened samples. It is supposed the nitrogen slows-down the oxygen diffusion into the metal. The extent of the oxygen-enriched metal is also smaller on LSP samples, which improves the ductility of titanium

Tracking the role of nitrogen in the improvement of the high temperature oxidation resistance of titanium by mechanical treatments

International audienceWe report the role of ultrasonic shot-peening (SP) and laser-shock peening (LSP) on the insertion of atmospheric nitrogen during high temperature oxidation of pure titanium and the improvement of its oxidation resistance. Ion Beam analysis showed that for short oxidation durations, a layer of Ti 2 N is formed at the oxide-metal interface. However, only the LSP treatment leads to the formation of a long-term stable nitrogen-rich layer which acts as a barrier for the diffusion of oxygen. This explains the efficiency of the LSP treatment to reduce the oxidation of Ti and prevent embrittlement