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An Rtec ball-on-disk tribometer was used to investigate the tribological performance of the synthesised water-based nanolubricants containing hBN/TiO2 nanocomposite at room temperature. The water-based nanolubricants with different concentrations were prepared by adding glycerol and sodium dodecyl benzene sulfonate (SDBS) under ultrasonication. These as-prepared nanolubricants demonstrated exceptional dispersion stability for 7 days without distinct sedimentation. The results indicate that the water-based nanolubricants with an overall concentration of 1.0 wt% at different ratios (hBN: TiO2 = (1:0), (0.7:0.3), (0.5:0.5), (0.3:0.7), (0:1)) can effectively reduce the coefficient of friction (COF) and the wear of the ball and disk. In particular, the water-based nanolubricant containing 0.5 wt% hBN and 0.5 wt% TiO2 exhibited the best tribological performance, leading to a significant reduction in COF up to 70%, and decreased the wear area of the ball and disk by up to 79.57% and 60.40%, respectively, compared to those obtained using distilled water. The lubrication mechanisms were mainly attributed to the formation of a protective film, and the mending, polishing, rolling, and synergistic effects of the hBN nanosheets and TiO2 nanoparticles. [ABSTRACT FROM AUTHOR]

In recent years, medium manganese steels (MMSs) have garnered increased attention and interest due to their relatively low cost and superior combination properties compared to other steels. In particular, MMSs have been recognised as ideal wear-resistant materials employed in the mining industry. However, the studies on their wear performance have a lack of systematic documentation. This review provides an extensive overview of recent advances in the wear performance of MMSs, starting from discussions on applicable wear testing methods and typical wear testing results, followed by a further discussion on the wear mechanisms of MMSs based on five wear characteristics, including abrasive wear, adhesive wear, corrosive wear, fatigue wear and impact wear. The effects of hardness and hardened layers on the wear mechanisms are also discussed. Finally, the influence of phase constitution and microstructure on the wear performance of MMSs are comprehensively elaborated in terms of transformation induced plasticity (TRIP), twinning induced plasticity (TWIP), alloy elements and heat treatment. The key factors that affect the wear performance of MMSs include the elemental composition in MMSs and the phase transformation occurred during TRIP and TWIP as well as various heat treatment processes. The current review of key factors affecting the wear performance of MMSs sheds some light on new strategies to enhance the service performance and longevity of wear resistant steels in various engineering applications. [ABSTRACT FROM AUTHOR]

Bimetal composites have wide applications due to their excellent overall performance and relatively low comprehensive cost. The aim of this study is to investigate the forming behaviour of stainless/carbon steel bimetal composite during stamping by finite element method (FEM). In this work, the bonding interface of bimetal composite sheet was assumed to be perfect without delamination during the plastic forming process for simplicity. Uniaxial tensile tests on base metal (carbon steel) and compositing metal (stainless steel) were first carried out, respectively, in order to obtain the tensile properties of each of the component materials required in the forming simulation. Processing variables, including the layer stacking sequence, relative thickness ratios of two layers and friction were considered, and their effects on the distributions of circumferential stress and thickness strain were analysed. The bimetal composite sheet was set as the eight-node solid elements in the developed FEM model, which is effective for evaluating the distributions of circumferential stress and thickness strain, and predicting the high-risk region of necking during the stamping of bimetal composites. The simulation results can be used as an evaluation indicator of the capability of forming machine to ensure the bimetal composite can be safely formed.

The formation and performance of oxide scale on a low-alloy steel were investigated during hot rolling at 850 and 950 °C under various lubrication conditions, including benchmarks (dry condition and water) and water-based nanolubricants containing various concentrations of nano-TiO2 from 1.0 to 8.0 wt%. The results showed that the addition of nano-TiO2 particles in the lubricant significantly reduced the thickness of oxide scale and surface oxide roughness. The reduction reached the maximum when the concentration of TiO2 was 4.0 wt%. Detailed oxide phase characterisation and oxide component fraction determination revealed that hot rolling destroyed the conventional multi-layer oxide scale and promoted magnetite and haematite formation because of easy access of oxygen from the deformed structure. The effect of TiO2 was explained by the decrease in the rolling force, which led to a higher fraction of dense retaining wustite and therefore reduced the extent of further oxidation. Increasing temperature did not change the trend of lubrication effect but raised the rate of steel oxidation in general. [ABSTRACT FROM AUTHOR]