An analytical review of the effect of high-temperature thermomechanical treatment on the structure and properties of steels as a possible effective method of strengthening the teeth of excavator buckets. It is shown that the application of this method can have a positive effect not only on the hardness, but also on the entire complex of their mechanical characteristics, such as plasticity, impact toughness and fatigue resistance. In relation to Hadfield steel as the most frequently used material of the bucket teeth, it is noted that with increasing deformation grade of billets from 1 to 5, tensile strength of steel increases from 570 to 1030 MPa, yield strength – from 480 to 790 MPa, relative elongation – from 14.3 to 17.9 %, relative contraction – from 17.2 to 20.1 %, impact strength KCU – from 1.51 to 2.14 MJ/m2. This article presents the results of metallographic analysis and comparative tests for abrasive wear of Hadfield steel samples after typical heat treatment practiced at bucket teeth manufacturers and thermomechanical treatment. It is established that high-temperature plastic deformation of steel samples before quenching increases their wear resistance by 1.7 times. The authors attribute the detected increase in wear resistance to the formation of fine martensite in the surface layers of steel with a needle size of 3-10 nm, which increases its hardness by 47%. It is concluded that the presence of fine martensite in the structure of Hadfield steel can increase the service life of excavator bucket teeth made of this material. The results of this study are planned to be used in the development of an improved technological process for manufacturing bucket teeth of excavators.

Improving energy efficiency is considered to be important and cost-effective strategies to reduce greenhouse gas emissions, which is crucial in the face of global climate change. This study hypothesizes that there are significant differences in the impact of energy efficiency on economic and energy systems. Using quantile regression method, the impact of economic and energy characteristics on energy-related greenhouse gas emissions in 120 countries over the period 2010–2020 is investigated. Detailed analyses are conducted by dividing the countries into 12 groups based on gross national income per capita (Atlas method) and the share of resource rents in gross domestic product. A macro-level system of indicators for assessing energy efficiency is proposed, which can be linked to the economic and energy characteristics of the systems: National Energy Efficiency, Energy Intensity Ratio, Primary Energy Production Efficiency, Industrial Sector Energy Efficiency, Share of Low Carbon Energy, Population Energy Efficiency. The findings show that (1) global energy efficiency has remained largely unchanged over the decade; (2) there are differences in energy efficiency between fossil fuel producing and non-fossil fuel producing countries; (3) the factors that have an inverse effect on emissions in fossil fuels dependent countries include industrial energy efficiency and population energy efficiency, which are far from exhausting their potential; (4) despite the recognized importance of energy efficiency, its impact on reducing greenhouse gas emissions globally has been unnoticeable. The study highlights that Sustainable Development Goals 7 and 13 on energy affordability and emission reductions are conflicting and require harmonization of mechanisms to achieve them, such as balancing climate change mitigation investments, identifying the potential for energy efficiency improvements across economy or improving energy saving practices. The overall conclusion suggests that there is an urgent need to review current decarbonization and energy efficiency initiatives, given the lack of significant global progress in reducing greenhouse gas emissions or improving energy efficiency between 2010 and 2020.

This paper studies the effects of pipeline inner surface materials on hydrotransport energy parameters in the transportation of tailings slurry. It has been established that pipelines with inner surfaces made of polymeric materials ensure higher transportation energy efficiency due to lower specific pressure losses. The respective laboratory tests were carried out in two stages. At the first stage, pressure losses in the transportation of pure water and the initial roughness of the pipe samples studied were experimentally established. At the second stage, changes in sample roughness were studied in the hydrotransport of tailings slurry. The samples were represented by pipes made of high-density polyethylene with an inner layer of thermoplastic vulcanizate; single-layer pressure pipes manufactured in compliance with GOST 18599; and previously used longitudinally electric-welded steel pipes under GOST 10704-91. The influence of the hydraulic friction coefficient on the specific pressure loss and energy intensity of the hydrotransport process has been analyzed. Equivalent roughness values have been established for pipelines made of polymer materials and steel. The relationship between the roughness height parameters of Ra, Rq, Rz and the equivalent even-grained roughness has been established; their changes during tailings slurry hydrotransport ha