In recent years, the demand for high spatial resolution in X-ray residual stress analysis has drastically increased. The locations of interest are frequently small foot radii of teeth of gears. Also the inner surface of holes or hollow cylinders in general with small diameter must be investigated after opening the cylindrical cavities. In resolving such measuring problems, significant progress has been made in reproducibly manufacturing and applying glass capillary X-ray optics. With focusing elliptical polycapillaries and conventional laboratory X-ray sources, spot sizes of few 10 μm can be realized at sufficiently intensities for residual stress analyses. However, glass capillary optics require refined alignment strategies which are completely different from those for conventional beam shaping optics. Moreover, the small spot sizes cannot be aligned and positioned on the sample surface by eye. Microscopy fixtures are required. Finally, measurements in small radii result in high precision requirements for the diffractometers as well as for the sample positioning in axes and directions which are significantly less relevant when measuring on plane surfaces. The specific requirements resulting from residual stress analyses with high spatial resolution using glass capillaries and small spot sizes at curved surfaces are described and discussed.

The present work describes a systematic investigation of the influence of short-term tempering on the microstructure and mechanical properties of a fast solidified Fe84.3Cr4.3Mo4.6V2.2C4.6 (at.%) alloy. The applied casting conditions promote the formation of non-equilibrium phases such as martensite, retained austenite and a complex network of fine carbides already in the as-cast state. Additional short-term tempering further increases the strength and hardness of the alloy along with significantly improved ductility under compressive and tensile loading. By this procedure an extremely high ultimate compression strength of almost 4500 MPa combined with a compressive fracture strain of ∼22% and an ultimate tensile strength of over 1600 MPa can be achieved. The interacting mechanisms appearing due to short-term tempering were investigated by different X-ray diffraction methods and Auger electron spectroscopy, and a transformation of austenite into martensite as well as the formation of nano-carbides and a change in residual stresses during tempering was detected. Altogether, the outstanding properties of the material combined with the energy-efficient manufacturing process for Fe84.3Cr4.3Mo4.6V2.2C4.6 open up a new possibility to obtain a high-strength and simultaneously adequately ductile alloy for advanced tool design.

Die Ergebnisse von Schwingfestigkeitsversuchen von Proben, die aus dem stark umgeformten Bereich von Spaltprofilen entnommen wurden, werden dargestellt. Im Fokus steht die Wirkung von Mittelspannungen und Kerben im Zusammenhang mit der vorhergegangenen Umformung. Der Eigenspannungszustand im Bauteil und in den untersuchten Proben wird beschrieben. Numerische Analysen der Schwingfestigkeitsversuche an den Proben unter Berücksichtigung des Eigenspannungszustands ermöglichen es, den Einfluss von Eigenspannungen auf die Versuchsergebnisse rechnerisch zu analysieren. Zur Übertragung der an ungekerbten Proben ermittelten Kennwerte auf gekerbte, bauteilähnlichere Proben wird das Weibullsche Fehlstellen‐Modell angewendet.

The use of glass capillaries as primary optics for X-ray diffraction equipment and especially for X-ray stress analyses is frequently discussed as possibility to achieve a small irradiated area for investigations of micro systems and a reasonably high X-ray intensity in order to keep the measuring time within reasonable limits. These aims, however, can generally not be reached to a satisfying extent due to physical and experimental obstacles. The major drawbacks are the limited brilliancy of the available X-ray tubes and the large divergence of the X-ray beam exiting conventional cylindrical capillaries.A novel concept of X-ray capillary is presented which allows an efficient variation of the X-ray spot size on the sample and enables to reduce the irradiated area down to few 10 mum, even when using conventional X-ray tubes. At the same time, the presented capillaries offer a more than one order of magnitude higher intensity than conventional capillaries delivering comparable spot sizes.

A series of measurements has been performed on the neutron strain scanner of the Laboratoire Leon Brillouin in order to explore the limits of the spatial resolution achievable by neutron stress analysis. Two types of samples were investigated, i.e. sandwich structures consisting of thin sheets of copper and aluminum nitride (AIN) and shot peened steel sheets. With slits before and after the sample as small as 0.3 × 10 mm2 (AIN) or even 0.15 × 10mm2 (steel) counting times were not longer than 1–2 h/peak. Checks revealed that a spatial resolution of ≈0.3 mm (AIN) resp. 0.15 mm (steel) was indeed achieved in the direction perpendicular to the surface. Using partial immersion of the gauge volume, near-surface/interface strains could be explored with even higher spatial resolution, down to ≈30 μm in the case of steel. The stress gradients determined by neutron diffraction were checked by measurements using other techniques.

Thin plates of AIN were joined with Cu sheets by active brazing, and the residual stresses generated by the brazing process were investigated by neutron and X-ray diffraction. Residual stresses with values between 100 MPa and - 150 MPa were found in the ceramic layers. The residual stresses in the Cu layers had to be inferred from the balance of forces, because coarse grain effects and a strong variation of the stress-free lattice constant across the thickness due to interdiffusion of the brazing metal and the Cu layer did not allow to obtain reliable residual stress values by diffraction methods. The results are discussed with regard to failure of the joints due to cracking.

La repartition des textures sur l'epaisseur de l'echantillon dans du fer « armco » lamine a froid ete examine par diffraction des rayons X. Contrairement a la litterature, l'echantillon en fer armco d'un taux de laminage a froid final d'environ 67% analyse ici presente une repartition complexe des textures a travers la section Dans le domaine proche de la surface se trouve une texture typique des materiaux cubiques-centres lamines a froid, caracterisee par une composante {001} etalee de ±60° autour de l'axe Dans les domaines inferieurs, soumis a un cisaillement modere, on trouve une texture de Goss essentiellement caracterisee par des orientations cristallographiques autour de {110} . Elle a son maximum d'intensite a environ 25% de l'epaisseur de l'echantillon Au coeur de l'echantillon, ou le cisaillement disparait pour des raisons de symetrie, une texture fibreuse avec l'axe de la fibre perpendiculaire a la surface de l'echantillon domine, accompagnee d'une composante de texture de laminage de type {001} comme en surface. Les transitions entre les differentes composantes sont progressives.

The depth distribution of the crystallographic texture of a cold rolled low carbon steel was investigated using X-ray diffraction. In contrary to literature, the material under investigation showed a complex distribution of the texture with depth. At and near the surface a typical rolling texture {001}<110> with a spread of about +/-60 degrees around the <110> axis was found. In deeper regions, the rolling texture was followed by a Goss texture {110}<001> with a maximum at 25% of the thickness below the surface. In the sample centre, however, a <111> fibre texture with the fibre axis in normal direction and a small amount of a {001}<110> rolling texture were observed. Between these texture components smooth transitions occur.

Joining of cemented carbide cutting edges and tool bodies of steel by brazing creates residual stresses in the joints due to the thermal mismatch of the components during cooling from brazing temperature. Such residual stress states can cause early failure of the tools by cracking of the cutting edge under quasi-static or cyclic loading conditions. In order to characterize the residual stress states occurring in brazed cutting tools of steel and cemented carbide, cemented carbide cutting edges were brazed into steel bodies of different types of steel. A combination of numerical and experimental methods was applied for the analysis of the resulting residual stress states. The influence of the phase transformation behavior of the steel body on the residual stress development was demonstrated. The failure behavior of the joints was explained by superposition of residual and loading stresses.

The mechanical response of as-received thermal barrier coating specimens with three different microstructures was evaluated. Specimens consisted of rectangular bars of Inconel 617 substrates with NiCoCrAlY bond coats and EB-PVD zirconia top coats. The deposition conditions had been varied to produce columnar top coat microstructures with three different column sizes. Scanning electron microscopy, optical microscopy, and X-ray diffraction analyses were used to characterize the microstructures. Four-point bend experiments were performed with the top coat under either tension or compression. In situ microscopy identified the damage formation and propagation modes, and acoustic emission analyses also identified differences in the responses of each microstructure.

Grinding residual stress states in Al2O3 and AlN were investigated by means of X-ray diffraction using a conventional Bragg-Brentano geometry as well as an advanced quasi-parallel beam set-up. Depending on the grinding conditions, steep near-surface residual stress gradients were found and discussed with respect to the grinding process. Furthermore, it could be proved, that residual stress analyses performed in quasi-focussing Bragg-Brentano geometry cannot resolve residual stress maxima or huge changes of the residual stress state near the surface [1]. In contrary, X-ray residual stress analyses using a quasi-parallel beam allow a highly resolved determination even of steep graded grinding residual stress states.

Thin hard coatings are commonly used to enhance the wear resistance of cutting, broaching and shaping tools for steel machining. PVD-processes used for deposition on various kinds of tools offer the opportunity to control the constitution and microstructure as well as residual stresses of the coatings by adjusting appropriate process parameters. Beside the microstructure the residual stress states strongly influence in-service performance of the coatings and are therefore important to assess and to correlate with process parameters. A special approach was employed to non-destructively determine the gradients of residual stresses and stress-free lattice parameters over, the thickness of graded PVD-Ti(C,N) wear resistant coatings by means of X-ray diffraction. To evaluate the mechanical properties of the coatings they were tested by recording load-indentation curves using spherical indenters to yield concentric cracking. Combining results from FEM-analyses of indentation tests with results of X-ray residual stress analyses the fracture-initiating radial stresses were determined and the mode-I fracture toughness of the coating material could be estimated using a simple fracture criterion.

Plates of cemented carbide were joined to steel by brazing. The structure was designed in imitation of a rock drill. Two types of steel were used which, after cooling from brazing temperature, showed a normalized ferritic–perlitic or a martensitic material state, respectively. Copper foil containing a nickel mesh was used as braze material. The residual stresses resulting from the different thermal shrinkage and elastic–plastic behavior of the materials as well as from the different phase transformation behavior of the steels during cooling of the samples from the brazing temperature (1100℃) to room temperature were investigated by neutron diffraction with special attention to the regions near the interface between steel and cemented carbide. Additional measurements were performed by X-ray diffraction on selected surface areas. Most of the experimental results could be satisfactorily modelled by three-dimensional finite-element calculations employing the temperature dependent elastic–plastic behavior of the materials. In particular, characteristic differences between the residual stress states of components with ferritic–perlitic or martensitic steel bodies were found experimentally as well as by the model calculations. Some points are discussed which require further investigations.

Thin hard coatings are widely employed in order to improve the efficiency of cutting and forging processes by increasing wear and corrosion resistance of the tools. Recent investigations have shown that PVD-gradient coatings of Ti(C,N) on cutting edges of cemented carbide exhibit a significantly greater wear resistance than conventional TiC or TiN coatings. However, beside the microstructure and composition the residual stress state in the coatings strongly influence the in-service performance. In addition to TEM and SEM investigation on the microstructure, X-ray residual stress analyses on Ti(C,N)-gradient coatings were performed. The special approach employed for the non-destructive depth-resolved determination of the residual stress states and stress-free lattice parameters in the gradient coatings is presented together with results obtained from selected Ti(C,N)-gradient coatings.

AlN is of increasing importance as structural material in microelectronics and microsystems in order to replace Al2O3. However, the knowledge of mechanical properties of this material is still restricted, and an enhanced understanding about the material behaviour of AlN requires the knowledge concerning the residual stresses. In order to determine the residual stresses by means of X-ray diffraction, X-ray elastic constants are needed which account for the elastic anisotropy and the coupling conditions of the crystallites in the polycrystalline material. Therefore, the X-ray elastic constants of AlN were determined for selected lattice planes {hkl} by X-ray diffraction. From the single crystal elastic constants calculated on the base of this knowledge, the X-ray elastic constants were derived for all sets of lattice planes {hkl} of interest. Employing these data, X-ray residual stress analyses were performed on differently machined samples of AlN.