Abstract In this paper, ultrasonic surface rolling processing (USRP) was used to strengthen GCr15-bearing steel. A finite element three-dimensional model of USRP was established to analyze the residual compressive stress and equivalent plastic strain distribution on the bearing steel surface. The microstructure, hardness, surface roughness, and corrosion resistance before and after USRP treatment were characterized by SEM, EBSD, X-ray diffraction (XRD), and electrochemical techniques. Results indicated that USRP treatment can significantly improve the material's surface microstructure and residual compressive stress distribution and obtain a plastic strain layer of about 60μm. After USRP treatment, the Kernel Average Misorientation (KAM) increased, and the dislocation activity was more intensive, resulting in aggregation near grain boundaries, and the percentage of LAGBs increased to 38.8%. Under the combined effect of surface grain refinement, residual compressive stress, and high glossy surface, the self-corrosion current density is reduced by two orders of magnitude, and the corrosion resistance is significantly improved. This investigation suggests a solution to the bearing failure problem and has implications for understanding the deformation mechanism of ultrasonic surface rolling processing.

Optimally designed bone implants with a suitable porous structure have similar mechanical properties to bone tissue and at the same time have good biocompatible and excellent bioactivity. The preparation of medical biological porous scaffolds by metal 3D printing technology is one of the most promising and attractive biomedical applications. The traditional regular porous and self-growing porous scaffolds were established by using CAD and C4D software, and the different scaffolds of three-dimensional models in similar porosity was obtained. A three-dimensional model of a scaffold with a porous structure was designed, and the porous scaffold was prepared by selective laser melting (SLM) technique, and its microstructure and mechanical properties were analysed. Under the similar porosity, the average hardness of the surface of the self-growing structure porous scaffold reached 236.5HV, and the stress at 5% compressive strain after heat treatment was close to 75 MPa. The original surface of the 316L porous scaffold made by SLM has the potential to effectively promote the differentiation of MG63 cells into osteoblasts. At the same time, the surface morphology and structure of the self-growth scaffold are similar to human cancellous bone, which is conducive to cell attachment and growth, so it is more suitable for repairing diseased parts of human bones.

Nano-surface layers were prepared on the surface of 6061 aluminum alloy using the ultrasonic surface rolling process (USRP). The surface morphology, surface roughness, microstructure, hardness, and corrosion resistance of 6061 aluminum alloy were systematically characterized using X-ray diffraction (XRD), laser scanning confocal microscopy (LSCM), optical microscope(OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and other testing methods. The results showed that ultrasonic surface rolling strengthening did not change the surface phase composition of 6061 aluminum alloy. It changed the size of the surface phases and the distance between the phases while refining the surface grains. The static pressures has a great influence on the surface properties of 6061 aluminum alloy. The best surface properties were obtained under 500N static pressures. The surface hardness reached 129.5HV0.5, the surface morphology was flat and continuous, the surface roughness was reduced to Ra0.191μm, and the corrosion resistance was significantly improved.