Search Results (26)

The aim of the research was to analyse the impact of peening each of the beads on the properties of a butt joint made of S960QL steel welded with ceramic backing on a robotic workstation using the 135 (MAG) method, and to determine the impact of pneumatic needle peening on the stress level. This analysis was based on a comparison of three butt joints: in the as-welded state, with each weld bead peened and post-weld heat treatment—stress relief annealing—performed. High-frequency peening (90 Hz) of each weld was performed to reduce stresses in the welded joint by introducing tensile stresses into it. A Weld Line 10 pneumatic hammer from PITEC GmBH was used for this purpose. The test joints obtained were tested in accordance with the requirements of EN ISO 15614-1. In order to determine the state of residual stresses, stress measurements were carried out using the Barkhausen effect based on the testing procedure of the technology supplier, NNT. This meter measures the intensity of the Barkhausen effect using a standard probe (with a single core). In order to verify the stress measurement using the Barkhausen method, stress measurements were performed using the XRD sin 2ψ technique based on the X’Pert Stress Plus program, which contains a database of material constants necessary for calculations. Structural studies, including phase analysis and crystallographic grain orientation, were performed using the backscattered electron diffraction method with a high-resolution scanning electron microscope and an EBSD (Electron Backscatter Diffraction) detector, as well as EDAX OIM analysis software. In addition, X-ray diffraction testing was performed on a Panalytical X’Pert PRO device using filtered cobalt anode tube radiation (λ = 1.79021 A). Qualitative X-ray phase analysis of the tested materials was performed in a Bragg–Brentano system using an Xcelerator strip detector. The tests showed that the high-frequency peening of each bead did not cause negative results in the required tests during qualification of the S960QL plate-welding technology compared to the test plates in the as-welded and post-stress-relief heat treatment states. Interpass peening of the weld face and HAZ resulted in a reduction in residual stresses after welding at a distance of 15 mm from the joint axis compared to the stress measurement result for the sample in the as-welded condition. This allows for a positive assessment of peening in terms of reducing the crack initiator in the form of the concentration of tensile stresses in the area of the fusion line and HAZ. Full article

The test method for internal stress of titanium-based nitride was optimized via penetration depth and surface roughness. Through the test method, the variations in the mechanical properties due to the ratio of the carbon gradient layer were investigated in terms of internal stress. TiN coatings were deposited on SUS 304 using RF/DC magnetron sputtering, and the penetration depth was adjusted by varying the X-ray power of HR-XRD for test specimens with the same coating thickness of 1 μm. The gradient of diagram for internal stress remained constant regardless of the penetration depth, and this was attributed to the analysis of internal stress focusing on the preferred growth orientation of the coating and excluding the influence of the substrate. In addition, we tested different surface roughness values (0.01 Sa, 0.02 Sa, and 0.03 Sa) to observe the effect on internal stress measurement. The results showed negligible difference in internal stress, confirming that this measurement method is valid for coatings with a surface roughness of 0.03 Sa or less. The test method was applied to analyze the carbon-doped TiZrN coating. TiZrN coatings were deposited on SUS 304, and coating thicknesses of 0.5 μm, 1 μm, and 2 μm were used to control the ratio of the carbon gradient layer. After applying the carbon paste for carbon doping, the TiZrN coating was irradiated with a pulsed laser. The compressive internal stress increased from −1263 MPa to −1687 MPa at a coating thickness of 0.5 μm, where the ratio of the carbon gradient layer was the highest. It was confirmed that the increase in internal stress with the ratio of the carbon gradient layer improved the mechanical properties of the carbon-doped TiZrN coating by laser carburization. Full article

The present study reports the tribological properties and residual stress of titanium chromium nitride (TiCrN) coatings. Thin films of TiCrN were deposited on tungsten carbide substrates at 400 °C in a vacuum of 5 × 10⁻⁶ mbar using the cathodic-arc physical vapor deposition technique with chromium variation. X-ray diffraction (XRD) spectroscopy was employed to probe the structures of the deposited thin films. The phase constituent was found to gradually shift from cubic TiN to cubic CrN. Both the hardness and elastic modulus of the sheet changed from 29.7 to 30.9 GPa and 446 to 495 GPa, respectively. The biaxial compressive residual stress after an initial absolute scan in the range of 30–100° was determined using XRD (d-sin²ψ method). These mechanical and tribological properties of films were investigated with the help of instrumented nanoindentation and a ball-on-disk tribometer wear test. The wear test indicates that the TiCrN thin film, featuring a Cr/Ti ratio of 0.587, exhibits superior wear resistance and maximum compressive residual stress in comparison to other thin films. Full article

Metal additive manufacturing processes induce residual stress in as-built components. These residual stresses are detrimental to part quality as they can induce defects such as warping and delamination. In some cases, when complex components are built, residual stress can even cause a build job to fail due to the recoater crashing into the distorted part. In this paper, the residual stress values of Ti6Al4V and Ti-6Al-2Sn-4Zr-6Mo alloys were evaluated by the cantilever approach and by the X-ray diffraction sin²(Ψ) method. The results showed that, as expected, Ti6Al4V as-built cantilevers displayed high distortion and von Mises equivalent stress values up to 494 MPa. On the contrary, as-built Ti-6Al-2Sn-4Zr-6Mo cantilevers were characterized by almost null warping and a residual stress value in the as-built state of 191 MPa. This different behavior is mainly due to the different properties of the hexagonal α’ martensite in Ti6Al4V and the soft orthorhombic α’’ martensite in Ti6246. The post-processing heat treatment significantly reduced the residual stress in Ti6Al4V, lowering it to 44 MPa, while, in the case of Ti-6Al-2Sn-4Zr-6Mo, the post-processing heat treatment did not affect the residual stress conditions. These findings suggest that Ti-6Al-2Sn-4Zr-6Mo could be a suitable candidate for the additive manufacturing production of extremely complex parts, as it could reduce the risks associated with recoater crashes and job failures. Full article

This work explores the advantages and disadvantages of a methodology using high-energy X-ray diffraction to determine residual stresses in multilayer structures produced by atmospheric plasma spraying. These structures comprise a titanium alloy substrate (Ti64), a bonding layer (Ni-Al), and an abrasive coating (Al₂O₃). This study focuses on analyzing the residual stress gradients within these layers. The presented method is used to determine stresses across the entire thickness of multilayer structures. Experiments were carried out using a high-energy rectangular beam, operating in transmission mode, on the cross-section of the sample. The results indicate variable stresses throughout the depth of the sample, particularly near the layer interfaces. The semi-automatic methodology presented here enables us to follow stress evolution within the different layers, providing indications of the load transfer between them and at their interfaces. The sin²ψ method was used to analyze the diffraction data and to determine the stresses in each phase along the sample depth. However, interpreting results near the interfaces is complex due to the geometric and chemical effects. We present a discussion of the main advantages and disadvantages of the methodology for this kind of industrial sample. Full article

The $\sin ²\psi$ method is the general method for analyzing X-ray diffraction stress measurements. This method relies on the estimation of a parameter known as $\frac{1}{2}{S}_2^{hkl}$, which is generally considered as a material constant. However, various studies have shown that this parameter can be affected by plastic deformation leading to proportional uncertainties in the estimation of stresses. In this paper, in situ X-ray diffraction measurements are performed during a tensile test with unloads on a low-carbon high-strength steel. The calibrated $\frac{1}{2}{S}_2^{hkl}$ parameter varies from $3.5\times {10}^{-6}$ MPa⁻¹ to $5.5 {\times 10}^{-6}$ Mpa⁻¹, depending on the surface condition and on the plastic strain state, leading to a maximum error on the stress level of 40% compared to reference handbook values. The results also show that plastic strain is responsible for 6 to 14% of the variation, depending on the initial surface sample condition. A method is then proposed to correct this variation based on the fit of the $\frac{1}{2}{S}_2^{hkl}$ evolution with respect to the peak diffraction width, the latter being an indication of the plasticity state. It is shown that the proposed methodology improves the applied stress increment prediction, although the absolute stress value still depends on pseudo-macrostresses that also vary with plastic strain. Full article

In this work, the deposition of β-Ga₂O₃ microstructures and thin films was performed with Ga(NO₃)₃ solutions by ultrasonic nebulization and spray coating as low-cost techniques. By changing the deposition parameters, the shape of β-Ga₂O₃ microstructures was controlled. Micro-spheres were obtained by ultrasonic nebulization. Micro-flakes and vortices were fabricated by spray coating aqueous concentrated and diluted precursor solutions, respectively. Roundish flakes were achieved from water–ethanol mixtures, which were rolled up into tubes by increasing the number of deposition cycles. Increasing the ethanol-to-water ratio allows continuous thin films at an optimal Ga(NO₃)₃ concentration of 0.15 M and a substrate temperature of 190 °C to be formed. The monoclinic β-Ga₂O₃ phase was achieved by thermal annealing at 1000 °C in an ambient atmosphere. Scanning electronic microscopy (SEM), X-ray diffraction (XRD), and UV-Raman spectroscopy were employed to characterize these microstructures. In the XRD study, in addition to the phase information, the residual stress values were determined using the sin²(ψ) method. Raman spectroscopy confirms that the β-Ga₂O₃ phase and relative shifts of the Raman modes of the different microstructures can partially be assigned to residual stress. The high-frequency Raman modes proved to be more sensitive to shifting and broadening than the low-frequency Raman modes. Full article

In order to reveal the relationship between residual stress in Si layers of SiC/SiC composites and the different parameters used in their preparation, the residual stress of the coating surface was tested using X-ray sin²ψ technology and laser Raman spectroscopy. Then, the Raman shift–stress coefficient (P) and the Raman shift with free stress (ω₀) were calculated as −201.41 MPa/cm⁻¹ and 520.591 cm⁻¹ via linear fitting with the least squares method. The results showed that all the as-sprayed Si coatings exhibited tensile stress on the surface, ranging from 53.5 to 65.9 MPa. The parameters of the spraying distance and second gas (H₂) flow rate were considered to be the most important for controlling the residual stress on the coating surface. Additionally, the surface tensile stress of the Si layers could be eliminated and even changed into compressive stress by annealing above 800 °C. Furthermore, the residual stress distribution in the cross-section of the Si layers was evaluated using laser Raman spectroscopy. Additionally, the particle characteristics, such as in-flight velocity and temperature, were investigated using a diagnostic system. The results of this research contribute to increasing the understanding and control of residual stress in APS Si bond layers. Full article

This work deals with non-linear $d^{hkl}$−${sin}^2\psi$ distributions, often observed in X-ray residual stress analysis of plastically deformed metals. Two different alloys were examined: duplex stainless steel EN 1.4362 with an austenite:ferrite volume ratio of 50:50 and ferritic stainless steel EN 1.4016. By means of an in situ experiment with high-energy synchrotron X-ray diffraction, the phase-specific lattice strain response under increasing tensile deformation was analysed continuously with a sampling rate of $0.5$ Hz. From Debye–Scherrer rings of nine different lattice planes {hkl}, the $d^{hkl}$−${sin}^2\psi$ distributions were evaluated and the phase-specific stresses were calculated. For almost all lattice planes investigated, oscillating courses in the $d^{hkl}$−${sin}^2\psi$ distributions were observed, already occurring below the macro yield point and increasing in amplitude within the elasto-plastic region. By comparing the loaded and the unloaded state after deformation, the contribution of crystallographic texture and plastically induced intergranular strains to these oscillations could be separated. For the given material states, only a minor influence of crystallographic texture was observed. However, a strong dependence of the non-linearities on the respective lattice plane was found. In such cases, a stress evaluation according to the ${sin}^2\psi$ method leads to errors, which increase significantly if only a limited $\psi$ range is considered. Full article

Additive manufacturing (AM) has seen remarkable development in recent years due to relatively high efficiency of the process. Cold spraying (CS) is a particular method of AM, in which titanium and titanium alloy powders are used. CS is a very competitive technology enabling the deposition of coatings, repairing machine parts, and manufacturing new components. For specific applications, the surface of cold-sprayed materials may require further processing. This paper reports an attempt to employ laser surface treatment (LST) of cold-sprayed coatings on an aluminium alloy substrate. The influence of laser beam interaction time on the coatings’ properties was analysed. The microstructure was investigated and observed employing scanning electron microscopy (SEM). To evaluate residual stress after CS and LST, the sin²ψ technique was used. Investigations were also performed on Vickers hardness, contact angle, and surface roughness. Significant changes in the surface morphology of the coatings and elevated residual stress levels dependent on the laser beam interaction time were observed. Increased Vickers hardness was recorded for titanium alloy Ti6Al4V. LST also led to increased surface hydrophilicity of the modified materials Ti and Ti6Al4V. Full article

In this paper, a portable residual stress tester and synchrotron radiation diffraction technique were used to measure the residual stress distribution of thick 2A14 aluminum alloy plates under different aging conditions after solution treatment. The stress changes after solution and aging were analyzed using metallographic structure observation, electron backscattered diffraction (EBSD), X-ray diffraction (XRD), and other characterization methods. The results show that after solution treatment at 500 °C and aging at 170 °C, the second phase precipitates, lattice distortion is released, and the stress level gradually decreases with aging time. The residual stress of the plate comprises compressive stress; there is stress concentration in the central area. The stress distribution obtained by the two residual stress calculation methods, cosα and sin²ψ, under different process conditions was consistent. Full article

Ga-ion micro-ring-core FIB-DIC evaluation of residual stresses in shot peened VT6 (Ti-6Al-4V) alloy was carried out and cross-validated against other non-destructive and semi-destructive residual stresses evaluation techniques, namely, the conventional ${\sin }^2\psi$ X-ray diffraction and mechanical hole drilling. The Korsunsky FIB-DIC method of Ga-ion beam micro-ring-core milling within FIB-SEM with Digital Image Correlation (DIC) deformation analysis delivered spatial resolution down to a few micrometers, while the mechanical drilling of circular holes of ~2 mm diameter with laser speckle interferometry monitoring of strains gave a rough spatial resolution of a few millimeters. Good agreement was also found with the X-ray diffraction estimates of residual stress variation profiles as a function of depth. These results demonstrate that FIB-DIC provides rich information down to the micron scale, it also allows reliable estimation of macro-scale residual stresses. Full article

In this paper, three commercial cermet powders, WC-Co-Cr, WC-Co and WC-Cr₃C₂-Ni, were sprayed by the High Velocity Oxy Fuel (HVOF) method onto magnesium alloy AZ31 substrate. The coatings were investigated in terms of their microstructure, phase analysis and residual stress. The manufactured coatings were analyzed extensively using optical microscopy (OM), X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM). Based on microstructure studies, it was noted that the coatings show satisfactory homogeneity. XRD analysis shows that in WC-Co, WC-Co-Cr and WC-Cr₃C₂-Ni coatings, main peaks are related to WC. Weaker peaks such as W₂C, Co_0.9W_0.1, Co and W for WC-Co and W₂C, Cr₃C₂ and Cr₇C₃ for WC-Cr₃C₂-Ni also occur. In all cermet coatings, linear stress showed compressive nature. In WC-Co and WC-Cr₃C₂-Ni, residual stress had a similar value, while in WC-Co-Cr, linear stress was lower. It was also proved that spraying onto magnesium substrate causes shear stress in the WC phase, most likely due to the low elastic modulus of magnesium alloy substrate. Full article

Titanium Grade 4 (Ti G4) is widely used in medicine for dental implants. The failure-free life of implants depends on their properties such as resistance to wear and friction processes. This paper presents an analysis of the influence of sandblasting on tribological wear of commercial dental implants made of TiG4 in artificial saliva. Tribological wear measurements were performed in a reciprocating motion in the ball-on-disc system. The scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS) method was used to characterize the surface of the implants before and after the tribological wear test. The microhardness of Ti G4 was measured before and after sandblasting by the Vickers method. The contact angle was determined by the method of sitting drop in air. The residual stress test using the X-Ray Diffraction (XRD) single-{hkl} sin²ψ method was carried out. The compressive residual stress of 324(7) MPa and surface hardening of Ti G4 was revealed after sandblasting with Al₂O₃ particles of 53–75 μm in diameter. It was found that sandblasting changes the surface wettability of Ti G4. The intermediate wettability of the mechanically polished surface and the hydrophobicity of the sandblasted surface was revealed. Sandblasting reduces the tribological wear and friction coefficient of Ti G4 surface in saliva. The three-body abrasion wear mechanism was proposed to explain the tribological wear of Ti G4 in saliva. Full article

An integrated software for calculating the major mechanical properties of materials was newly programmed. The material mechanical properties are determined from a peak position and the broadness of X-ray diffraction (XRD) line using profile function method, including Gaussian, Parabola, Half-width, and Centroid. The X-ray diffraction line in software is also corrected by the generalized X-ray absorption function. The results show that the precision coefficient (R²) of the d_hkl-sin² ψ linear regression depends on tested materials and the method of the 2θ determination. The Parabola and Gaussian methods show greater fitting accuracy in comparison to the other two methods in determining stress. The mechanical properties calculated using this software agreed well with the values determined from the conventional methods. In addition, this XRD software also allows computing the 95% confidential limits of the results from a single measurement without conducting repetitive measurements. Therefore, the new software allows widening the experimental scopes of an X-ray diffraction device in both laboratories and the industrial sector. Full article