The purpose of this research was to analyze the change in residual stresses in the surface layer of steel samples taking into account the technological heredity effect on the value and sign of residual stresses. An installation of combined processing was developed. Combined processing consists of sequentially performing electromechanical processing and diamond smoothing. All areas of the samples were studied—after machining (i.e., in the initial state), after electromechanical processing, and after diamond smoothing. The research shows that the sign and value of residual stresses are significantly affected by the combined processing modes. The main parameters of the surface layer are formed at the final stage of the combined processing–diamond smoothing. This paper gives recommendations on the use of combined processing for power plant parts.

We have proposed and developed a method for measuring the thermal conductivity of highly efficient thermal conductors. The measurement method was tested on pure metals with high thermal conductivity coefficients: aluminum (99.999 wt.% Al) and copper (99.990 wt.% Cu). It was demonstrated that their thermal conductivities at a temperature of T = 22 ± 1 °C were <λ_Al> = 243 ± 3 W/m·K and <λ_Cu> = 405 ± 4 W/m·K, which was in good agreement with values reported in the literature. Artificial graphite (${\rho }_{\mathrm{G}1}$ = 1.8 g/cm³) and natural graphite (${\rho }_{\mathrm{G}2}$ = 1.7 g/cm³) were used as reference carbon materials; the measured thermal conductivities were <λ_G1> = 87 ± 1 W/m·K and <λ_G2> = 145 ± 3 W/m·K, respectively. It is well established that measuring the thermal conductivity coefficient of thin flexible graphite foils is a complex metrological task. We have proposed to manufacture a solid rectangular sample formed by alternating layers of thin graphite foils connected by layers of ultra-thin polyethylene films. Computer modelling showed that, for equal thermal conductivities of solid products made of compacted thermally exfoliated graphite and products made of a composite material consisting of 100 layers of thin graphite foil and 99 layers of polyethylene, the differences in temperature fields did not exceed 1%. The obtained result substantiates our proposed approach to measuring thermal conductivity of flexible graphite foil by creating a multi-layer composite material. The thermal conductivity coefficient of such a composite at room temperature was <λ_GF> = 184 ± 6 W/m·K, which aligns well with measurements by the laser flash method.

We have developed a technological process for obtaining compacted multi-graphene structures (CMGSs) with the thermal conductivity of 500 W/(m×K). We propose the “Soft” regime of graphite intercalation procedure, which yields conglomerates with alternating stacks of five graphene layers, while the “Standard” regime is characterized by the formation of alternating stacks of three graphene layers. X-ray diffraction analysis and transmission electron microscopy studies of Soft and Standard CMGS have shown that the thermal conductivity of these materials is limited by defect density, size distribution, and misorientation of nanocrystallites. The effect of micro-deformations and residual macro-stresses on thermal conductivity of CMGS is discussed. The Soft method facilitated the formation of CMGSs with a less disrupted internal structure, characterized by increased nanocrystallites and reduced misorientation angles relative to the Standard approach, resulting in a 38% enhancement in thermal conductivity. A refined model is proposed that incorporates these key structural factors governing heat transport in CMGSs. The proposed method made possible the preparation of CMGS-based material with a thermal conductivity 25% higher and with a density five times lower than those of copper. Our findings demonstrate that precise regulation of the intermolecular explosion parameters enables the design of lightweight, flexible carbon-based materials with engineered thermal conductivity characteristics for advanced thermal-management applications.

An automated system for measuring the thermal conductivity of functional and structural materials was developed. The main building blocks of the setup are the following: heating unit and cooling unit creating a heat flux gradient in the test sample; thermal resistances for temperature registration and control; and thermal pads for better contact between parts of the setup and the sample. The effect of the thermal conductivity of thermal pads and thermal resistances on the distribution of thermal fields in the developed setup was studied by computer modelling. A control software for the measuring setup was developed based on the hardware implementation of the steady-state Fourier’s law-based method for the determination of thermal conductivity. The stopping criterion for the setup control software is the equality of heat fluxes in the heating and cooling units, as well as the stability of the thermal conductivity coefficient readings. The testing and calibration of the device were carried out using a sample of pure aluminum (99.999 wt.% Al). It was found that the experimental value of the thermal conductivity coefficient of the aluminum sample at room temperature (T = 22 °C) is <λ> = 243 ± 3 W/m·K. This value of the thermal conductivity coefficient is consistent with the literature data and experimental values obtained by the laser flash method, which ranges within λ = 210–260 W/m·K.