The compact cast-rolling compound forming of bimetallic ring is an efficient process for manufacturing large bimetallic rings. The difference in hot deformation behavior of the two metals directly affects the coordinated deformation of bimetals during hot rolling. In this paper, hot compression tests of 40Cr/Q345B bimetallic blank produced by centrifugal casting were carried out at temperatures of 950–1200 °C and strain rates of 0.005–5 s⁻¹. Based on the comparisons of flow stress behavior, activation energy, and activation volume, hot deformation behavior coordination of 40Cr/Q345B bimetallic blank was investigated. Processing maps were established to study the optimum processing windows for 40Cr/Q345B bimetallic blank. Under the same deformation conditions, 40Cr shows lower overall flow stress than Q345B, which facilitate the coordinated deformation of the bimetallic blank during rolling, and the flow stress difference between 40Cr and Q345B decreases with the increase of temperature. It was connected with the increase in the second phase particles pinning effect for higher MnS content in Q345B. The common rate-controlling mechanism for 40Cr and Q345B is the thermal breaking of attractive junctions and movement of jogged screw dislocations. The bimetallic blanks exhibit good deformation coordination in the optimum processing window (1030–1100 °C and 0.5–1 s⁻¹ with a strain of 0.6).

This study aims to explore the effects of ultrasonic impact parameters on the surface modification of a stainless steel coating deposited on a medium-carbon low-alloy steel using argon arc surfacing welding. Ultrasonic impact treatment (UIT), at three different vibration strike numbers (40,000 times/(mm²), 57,600 times/(mm²), and 75,000 times/(mm²)) marked UIT–1, UIT–2, and UIT–3, respectively, was carried out to modify the surface structure and properties of the stainless steel coating. The surface morphological and structural features, phase compositions, grain size, topography, micro-mechanical properties, as well as the wear resistance of the coating before and after UIT with different impact parameters were experimentally investigated. The results of optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X-ray diffraction (XRD) analyses revealed that the grain refinement accompanied by the formation of the strain-induced α′–martensite occurred on the UIT-treated coating surface. With the increase in the vibration strike number, the surface grain size and roughness decreased, while the α′–martensite content increased. Micro-hardness after UIT was increased by about 19% (UIT–1), 39% (UIT–2), and 57% (UIT–3), and the corresponding wear rate obtained was decreased by 39%, 72%, and 85%, respectively. Significant improvements in wear resistance were achieved using UIT. However, an excessive vibration strike number on the per unit area (/mm²) might result in unwanted micro-cracks and delamination on the treated surface, deteriorating the performance of the coating. These findings validate that UIT parameters (such as the vibration strike number on per unit area) are of great importance to bringing about improvements in wear performance, and UIT is found to have a high potential in modifying the surface characteristics and optimizing the mechanical performances of the deposited coating for a wide range of potential applications.

20CrMnTi carburized steel is widely used in the manufacturing of gear transmission components. Gears often operate under complex working conditions that involve high pressure and temperature, and intermittent alternating loads. The material is frequently subjected to repeated compression and resilience cycles, which significantly affect dimensional accuracy and stability. This study investigates the influence of different temperatures and pressures on the compression resilience properties and microhardness of 20CrMnTi steel. The results indicate that temperature and pressure lead to a nonlinear increase in the compression curve, reduce resilience properties and the microhardness of the carburized layer, and affect the microhardness of the matrix. Microstructural analysis indicated that plastic deformation, carbide coarsening, and a lower elastic modulus led to the enlarged compression and diminished microhardness in the carburized layer. Work hardening, dynamic recrystallization, and plastic deformation in the matrix material weaken resilience properties and influence the distribution of microhardness in the matrix.