Materials Science Forum Vol. 652

Abstract: In-situ diffraction measurements were carried out on a tensile specimen of SUS304 stainless steel using a small autoclave at BL22XU at SPring-8. The temperature of circulating water in the autoclave was changed from room temperature to 561 K under ambient pressure and also under a pressure of 8.8 MPa. Tensile stress of 260 MPa was applied to the specimen at 561 K under 8.8 MPa, and a two dimensional strain distribution was obtained by calculation based on measured lattice spacings of the γ-Fe311 plane under various conditions. The interior region of the specimen showed higher strain compared with that on the surface region. After the tensile deformation in the autoclave, CT images of cross sections of the specimen were taken. Void-like images with about 50 μm in size were observed.

Abstract: For engineering components with cracks, it is very important to evaluate the reliability for fracture. The X-ray diffraction method is now widely used to measure non-destructively the loading and residual stresses in crystalline materials. Synchrotron radiation sources provide the X-rays with extremely high intensity as well as a narrow divergence. The high intensity X-rays with a narrow divergence enables stress measurements in a localized region. The strain distribution near the fatigue crack in the steel plate with ultrafine-grained surface layers, called SUF plates, was measured by the polychromatic X-ray from synchrotron radiation at SPring-8. The spatial resolution in the direction parallel to the crack propagation direction was 0.1 mm. The strain distributions at several applied stress levels were determined for six diffraction planes. The measured strain distribution was compared with the result calculated by the FE analysis. The average value of the measured strains for several diffraction planes agreed well with the calculated results.

Abstract: The structures of Cr-N films deposited by arc ion plating on steel substrates were investigated using a synchrotron radiation system that emits ultraintense X-rays. The Cr-N films were found to be mainly composed of {110} oriented CrN crystals, but they also had a small component of randomly oriented Cr2N crystals. The CrN220 diffraction shifts to a high diffraction angle as the annealing temperature increases. In contrast, the peak position of the Cr2N211 diffraction hardly changes with an increase in the annealing temperature up to 873 K. The ratio of nitrogen and oxygen to chromium at the film surface and inside in the film was estimated by Auger electron spectroscopy. After annealing at 973 K, the surface layer was oxidized, but the composition inside the Cr-N films (N/Cr = 0.83) remained unchanged. The residual stress in a 1600-nm-thick as-deposited CrN layer was found to be -11.0 GPa. The residual stresses of Cr-N films relaxed to thermal stress levels on annealing. However, the residual stress in the Cr2N layer could not be evaluated.

Abstract: Platinum and platinum alloys, due to their good electrical and mechanical properties, are commonly used in fields such as jewellery, catalysis and electronics. In this work, a two-layer system of Pt and V, deposited on Si substrates by electron beam deposition technique, were investigated amongst others for residual stress development in the coating. The investigation was carried out using diffraction techniques employing laboratory X-rays on the BRUKER D8 Discover instrument equipped with a High Star detector and analyzed with LEPTOS v6 software. The results showed the stress state to be tensile, relaxing significantly on annealing. In addition, complementary results of phase composition, and coating morphology will also be presented.

Abstract: Residual strains in plasma sprayed and heat-treated hydroxyapatite (HA) coatings deposited on a titanium alloy (Ti-6Al-4V) substrate were investigated by means of neutron diffraction. Strain measurements were performed in vertical scan (“z-scanning”) mode to provide a through thickness strain profile in the coating and substrate materials. Results are discussed in terms of the influence of heat-treatment on the residual strain profile of these biomedical coatings. This investigation concluded that the heat-treatment had a significant effect on the residual strain profile in HA coatings.

Abstract: In this study, the authors investigated the application of the area detector type method for the purpose of evaluating residual stress in tools having a V-groove. The specimen used was a shot-peened forming rack. This alternative method uses a diffraction ring and single incidence X-ray to clarify precisely and effectively complex stresses and stresses in narrow parts of the tools such as the teeth on the surface of the rack. In addition, the authors evaluated stress gradients generated after shot peening using synchrotron radiation (SR).

Abstract: Neutron diffractometer Engin-X at ISIS was used use in this study to investigate the residual stresses in a section of a multi-pass girth welded thick pipe, of nominal thickness 62 mm, which was made of a ferritic-martensitic steel denoted type P92. Measurements in such large component sections are rare, and have driven the neutron diffraction method to the edge of its capabilities. Significant stresses of over 150 MPa have been found in this pipe section, though post weld heat treatment has been performed. The influences of these welding residual stresses in components at operating temperatures are discussed in terms of their relaxation and high temperature fracture behaviour.