The purpose of this work is to investigate the effect of the WC content on the surface characteristics and nanoindentation behaviors of WC/Ni-based composite laser-clad coatings. Four NiCrSiBC coatings with WC wt% of 30%, 40%, 50%, and 60%, respectively, were clad on carbon steel substrates using a laser. The morphologies and phase compositions of four clad coatings were comparatively observed. In addition, the hardness and elastic modulus values of the four coatings were measured and quantitatively calculated. As a result, with the increase in WC, the coating grains were more refined. Meanwhile, cracks and WC particle breakage occurred in the 50–60% WC coatings, whereas this was not found in the 30–40% WC coatings. When the WC content increased from 40% up to 50%, the coating hardness and elastic modulus significantly increased. However, a further increase in WC from 50% to 60% did not result in considerable improvement in coating quality but considerably worsened the coating’s cracking behavior instead. Therefore, for WC/Ni-based composite coatings, a threshold exists for the WC content, and this value was 50% within the experimental scope of this study.

A set of ultrasonic burnishing equipment with two different burnishing tips was designed and manufactured, with which a series of experiments were performed to explore the effects of process parameters and burnishing tips on the surface integrity of austenitic stainless steel material being treated by ultrasonic burnishing (UB). Based on the experiment data, the two surface treatments, i.e. UB with ball tip and UB with roller tip, were comparatively assessed together with the other two surface machining methods of fine turning and grinding. As a further study, a microscopic FE model was built to investigate the three-dimensional transient stress and strain field inside the being treated material. It was found that parameter combination is determinative to surface finishing in UB process, and static pressure and burnishing pass are supposed to be the two most significant parameters for surface integrity of the treated sample. On the whole, roller tip is more preferable to achieve good surface enhancement than ball tip. The superposition of ultrasonic vibration leads to the dynamic change of the stress and strain field in UB, resulting in the oscillating propagation of stress wave inside the material, which gives explanation for the good performance of UB than that of conventional burnishing without ultrasonic.

With the in-depth research on high-entropy alloys (HEAs), most of the current research uses experimental methods to verify the effects of the main elements of HEAs on the mechanical properties of the alloys. However, this is limited by the long experimental period and the influence of many external factors. The computer simulation method can not only effectively save costs and shorten the test cycle, but also help to discover new materials and broaden the field of materials. Therefore, in this paper, the physical properties (such as lattice constant, density and elastic constant) of AlCo_xCrFeNi (x = 0, 0.25, 0.5, 0.75, 1) HEAs were calculated based on the first-principles calculation method and virtual crystal approximate modeling method. It is found that AlCo_xCrFeNi HEAs have the best hardness and toughness properties, with a Co content of 0.5~0.7. The research results can provide theoretical guidance for the preparation of HEAs with optimal mechanical properties.