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In this work, the contact force model and experiment methods were used to study the dynamic response and impact wear behavior of TP316H steel. The Flore model and the classic Hertz model were selected for comparison with the experimental results, and the model was revised according to the section parameters of the TP316H tube. The results show that there is a large difference between the models without considering the effect of structural stiffness on the impact system and the test results, whereas the revised model has a good agreement. With the rise in impact mass, the coefficient of restitution increases from 0.65 to 0.78, whereas the energy dissipation and wear volume decrease. Spalling, delamination, plastic deformation, and oxidative wear are the main impact wear mechanism of TP316H steel. [ABSTRACT FROM AUTHOR]

Based on the trabecular bone structure, a porous micro-arc oxidation (MAO) coating and a MAO/Al composite coating were fabricated on AZ31D Mg alloy. Surface morphology, cross-section morphology, coating composition, and coating thickness were observed by scanning electron microscopy, energy dispersive spectrometry, and x-ray diffraction. Then, force-dampening and energy-absorbing effects of the coatings were explored by a constant kinetic energy impact experiment, to explore their dampening stress and reducing vibration values applying in engineering structure subjected to impact or vibration stress. Results show that large plastic deformation and cracks formed in the AZ31D Mg alloy after impact, and the MAO coating hindered the formation of the defects due to its higher stiffness. In addition, MAO enhanced the energy-absorbing ability of the Mg alloy, which is beneficial for vibration reduction. However, the MAO coating had a rough and brittle surface, and when Al was used to protect it, its force-dampening effect, energy-absorbing effect, and plastic deformation resistance had the evolution trend approaching the Mg alloy substrate but with improved crack resistance. MAO can be an optimization method for enhancing the plastic deformation resistance and vibration reduction effect of Mg alloy as structure material, and Al can be used to enhance its crack resistance. [ABSTRACT FROM AUTHOR]

In this study, low velocity impact tests were performed to MoS 2 /Pb nanocomposite coating and its substrate (304-stainless steel, for comparison). The machine is controlled based on kinetic energy and can achieve dynamic response during the tests. The MoS 2 /Pb coating exhibits better impact wear resistance, as shown by its favorable dynamic response. The energy absorption ratio evolution of MoS 2 /Pb coating indicates there were several impact damage forms during the tests, which was relevant to varied dominant impact damage mechanisms. In addition, tests with varied impact conditions were conducted, and distinct results were obtained, revealing the effects of tests parameters. Moreover, comparative analysis between values obtained from the Hertz theory and the measured revealed that the yield strength of MoS 2 /Pb coating was approximately 686.5 MPa, and the substrate was always under elastoplastic deformation although its impact kinetic energy was the lowest. The low velocity impact morphology was characterized by fatigue delamination because of the shearing stress in the subsurface. [ABSTRACT FROM AUTHOR]

In the heat exchangers of sodium-cooled fast reactors, sodium flow can cause the tubes to vibrate, resulting in fretting wear damage due to the contact between the tubes (2.25Cr-1Mo steel) and their support plate (Gr5C12 alloy). In this work, the effects of temperature on the fretting wear behavior of a 2.25Cr-1Mo heat transfer tube on a Gr5C12 alloy rod were studied. The results showed that the coefficient of friction (COF) and wear volume increased first and then decreased with the increase in temperature. Moreover, 2.25Cr-1Mo showed great wear performance at high temperatures than at room temperature and 80 °C, because of the antifriction nature of the oxidative layer and the high hardness of the tribological transformed structure layer. As the temperature increased, material transfer and plastic deformation became increasingly obvious, but average wear depth decreased. This provides data support for the practical engineering application of 2.25Cr-1Mo steel at elevated temperatures. Wear mechanisms were found to depend modestly on temperature and largely on normal load. As temperature increases, the wear mechanism gradually changes from abrasive wear to adhesive wear. [ABSTRACT FROM AUTHOR]

Salt layer preparation on the contact surface of Ti6Al4V dovetail joint specimens using solid NaCl and Na 2 SO 4 deposition, the effect of hot salt layer on fretting fatigue properties of Ti6Al4V alloy at high temperature was studied. The maximum stress load and temperature are 10 kN and 500 °C, respectively. The results show that the average fatigue life of the base metal dovetail joint sample (BM sample) is 9.93×104, and the average fatigue life of the hot salt dovetail joint sample (HS sample) is increased to 69.9×104. The increase in fatigue life stems from the fact that the hot salt layer promotes the generation of thicker loose oxides on the surface of the Ti6Al4V alloy, besides, the lubricating effect of the oxide with higher hardness and the wear debris alleviates the fretting damage between the dovetail joint sample and the contact surface of the fretting pad. Fracture analysis shows that the hot salt layer does not change the crack initiation mechanism, and all of them show single crack source propagation and ductile fracture mechanism. Analysis of crack formation zone by electron back-scattered diffraction (EBSD), it is found that the presence of less dislocation distribution in the HS sample relative to the BM sample. The dislocations are more concentrated on the crack propagation paths and the fretting fatigue contact surfaces. This indicates that the BM sample produced more significant plastic deformation in the crack formation zone, accelerating crack initiation. The contact surface plastic deformation of the HS sample is small and the fretting fatigue life is enhanced. • The salt-coated dovetail specimens designed for high-temperature fretting fatigue testing. • The salt-coated specimens had longer life under high temperature fretting fatigue test compared to the matrix specimens. • The mechanism of improved fretting fatigue life of salt-coated specimens relative to matrix specimens. [ABSTRACT FROM AUTHOR]

Low energy laser shock peening (LE-LSP) with different energies was carried out at zirconium (Zr) alloy. Characterization and electrochemical corrosion behavior of Zr alloy after LE-LSP treatment were investigated. Results show that the surface profile of Zr alloy after LE-LSP treatment is rough due to the regular undulations on the surfaces. The hardness of Zr alloy increases after LE-LSP treatment because the grain size of Zr alloy is refined, and the plastic deformation generated on the surface induces the working hardening. A melting layer, plastic deformation layer, and transition layer are formed on Zr alloy after LE-LSP treatment. The dislocation entanglement is observed at the plastic deformation layer, which indicates that the dislocation slip is the main deformation mechanism of Zr alloy. The electrochemical corrosion resistance of Zr alloy after LE-LSP treatment is improved because of an increase in the grain boundary, which improves the activity of Zr alloy and is beneficial for forming passive films. • A melting layer, plastic deformation layer, and transition layer were formed on Zr alloy after LE-LSP treatment. • The dislocation slip is the main deformation mechanism of Zr alloy during LE-LSP process. • The increase in the grain boundary of Zr alloy after LE-LSP treatment is beneficial for forming passive films. [ABSTRACT FROM AUTHOR]

The impact wear test of 2.25Cr–1Mo steel against Gr5C12 alloy was performed at a controlled kinetic energy impact wear rig. The effect of temperatures (from 25 °C to 450 °C) on the impact wear damage mechanism was investigated. The contact force, energy absorption, and interface deformation during the impact process were recorded and analyzed in real time. Wear volume, morphology, and elemental distribution of the wear scars were used to characterize wear and tribo-chemistry behavior. Results demonstrate that at varied temperatures, the interface behavior of 2.25Cr–1Mo steel is different. With the rise in temperature, both the contact force, absorption energy, and wear volume first increase and then decrease. The explanation is that higher temperatures can modify the material's surface properties. Delamination, plastic deformation, and oxidative wear are the major mechanisms of impact wear, but the proportions of the three wear mechanisms differ at varied temperature. • The impact wear behavior of 2.25Cr–1Mo steel at elevated temperature was investigated. • The interface behavior of impact wear was analyzed. • The impact wear mechanism of 2.25Cr–1Mo steel at elevated temperature was discussed. [ABSTRACT FROM AUTHOR]