Comparison of mechanical and tribological properties of CrBN coatings modified by Ni or Cu incorporation

To compare the merits of Ni and Cu,the mechanical and tribological properties of CrBN coatings modified by Ni or Cu incorporation were studied.The results demonstrated that the CrBN–Cu coatings presented a lower friction coefficient than CrBN and CrBN–Ni coatings owing to the improved lubrication effect of the CuO layer originating from the tribochemical reaction.However,the hardness decline due to Cu incorporation was much greater than that of Ni incorporation.Thus,the CrBN–Cu coatings exhibited a higher wear rate than the CrBN coating.In contrast,the plastic deformation enhancement induced by Ni incorporation exceeded the hardness decline.Therefore,the wear of CrBN–Ni coatings partially turned to plastic deformation to present a lower wear rate than that of the CrBN coating.

Structure and tribocorrosion behavior of CrMoSiCN nanocomposite coating with low C content in artificial seawater

CrMoSiCN nanocomposite coatings with a low C content were prepared on Ti−6Al−4V using an unbalanced magnetron sputtering system,and their corresponding microstructures,mechanical properties,and tribocorrosion performance were evaluated in detail.The results revealed that the CrMoSiCN coating had a compact nanocomposite microstructure consisting of CrN and Mo2N nanocrystallites,(Cr,Mo)N solid solution,and Si−C−N amorphous phases.Moreover,the coating exhibited superior mechanical properties with a hardness of 28.6 GPa and an elastic modulus of 273 GPa,owing to the solid solution strengthening effect.The tribocorrosion test results showed that the dominant failure of the Ti−6Al−4V alloy was caused by the corrosion contribution to wear behaviors(synergistic effect).The CrMoSiCN nanocomposite coating could effectively alleviate the material loss caused by the synergistic effect of corrosion and wear behaviors,leading to pure wear behaviors during the entire tribocorrosion process.The corresponding tribocorrosion mechanisms under the open circuit potential and dynamic polarization conditions were discussed in terms of their tribocorrosion behaviors.

A River Flood and Earthquake Risk Assessment of Railway Assets along the Belt and Road

Mitigating the disaster risk of transportation infrastructure networks along the Belt and Road is crucial to realizing the area’s high trade potential in the future.This study assessed the exposure and risk of existing and planned railway assets to river flooding and earthquakes.We found that about 9.3%of these railway assets are exposed to a one in 100 year flood event,and 22.3%are exposed to a one in 475 year earthquake event.The combined flood and earthquake risk of physical damage to railway assets,expressed by expected annual damage(EAD),is estimated at USD 1438(between 966 and 2026)million.Floods contribute the majority of the risk(96%).China has the highest EAD for both floods and earthquakes(between USD 240 and 525 million in total).Laos and Cambodia are the countries with the highest EAD per km from flooding(USD 66,125–112,154 and USD 31,954–56,844 per km,respectively),while Italy and Myanmar have the highest EAD per km from earthquakes(USD 1000–3057 and USD 893–3019 per km,respectively).For the newly built and planned projects along the Belt and Road,the EAD is estimated at USD 271(between 205 and 357)million.The China–Indochina Peninsula Economic Corridor and China–Pakistan Economic Corridor have the highest absolute EAD and EAD per km,with EADs reaching USD 95 and USD 67 million,and USD 18 and USD 17 thousand per km,on average,respectively.For railway segments with high risks,we found that if the required adaptation cost within 20 years to realize a 10%increase of the railway quality is below 8.4%of the replacement cost,the benefits are positive.