Corrosion Properties of 34CrMo4 Steel Modified by Shot Peening

Microstructure and Mechanical Properties of Gradient Nanostructured Q345 Steel Prepared by Ultrasonic Severe Surface Rolling

In this work, ultrasonic severe surface rolling (USSR), a new surface nanocrystallization technique, is used to prepare gradient nanostructure (GNS) on the commercial Q345 structural steel. The microstructure of the GNS surface layer is characterized by employing EBSD and TEM, and the result indicates that a nanoscale substructure is formed at the topmost surface layer. The substructures are composed of subgrains and dislocation cells and have an average size of 309.4 nm. The GNS surface layer after USSR processing for one pass has a thickness of approximately 300 μm. The uniaxial tensile measurement indicates that the yield strength of the USSR sample improves by 25.1% compared to the as-received sample with slightly decreased ductility. The nanoscale substructure, refined grains, high density of dislocations, and hetero-deformation-induced strengthening are identified as responsible for the enhanced strength. This study provides a feasible approach to improving the mechanical properties of structural steel for wide applications.

A Cost-Effective Method for Preparing Robust and Conductive Superhydrophobic Coatings Based on Asphalt

The wide application of superhydrophobic materials is mainly hindered by the poor mechanical robustness and complicated preparation method. To overcome these problems, we tried to make a combination of hierarchical and self-similar structure by the means of a simple spraying method. By adding nanofiller (carbon nanotube) and microfiller (graphite powder and expanded graphite), the hierarchical structure was constructed. By further doping the fillers in the commercial asphalt uniformly, the self-similar structure was prepared. Based on the aforementioned work, the as-prepared sample could withstand the sandpaper abrasion for 12.00 m under 4.90 kPa. Moreover, this superhydrophobic coating demonstrated good conductivity, superior self-cleaning property, and excellent corrosion resistance. The integration of conductivity with the superhydrophobicity might open new avenues for ground grid applications.

Residual Stress and Microstructure Characterization of 34CrMo4 Steel Modified by Shot Peening

34CrMo4 steel is widely used for drill stem in oil exploration, because of its excellent properties, such as favorable hardenability, shock absorption, less tendency of temper brittleness, and eminent wear resistance. In this study, the main works are residual stress test and microstructure characterization of 34CrMo4 steel upon various shot peening treatments. The residual stress distribution with effect depth was studied upon the shot peening. Face-to-face paste sample preparation method is required for continuous observation for microstructure evolution of shot-peened specimen from the treat surface to matrix. Grain refinement, lath structure, and precipitates are clearly observed in the gradient deformation layer.