This study investigates the tribological properties of 17-4PH martensitic stainless steel modified by plasma-based low-energy nitrogen ion implantation to enhance its surface hardness and wear resistance. The steel was nitrided at temperatures of 350 °C, 450 °C, and 550 °C for 4 h, and the resultant layers were characterized with respect to microstructure, hardness, and composition. Tribological tests were performed using a ball-on-disk tribometer under dry sliding conditions against an Si3N4 ceramic ball, with normal loads of 2-8 N and sliding speeds of 0.15-0.60 m/s. The results demonstrate that the nitrided layer thickness increased from 11 μm to 27 μm and the surface nitrogen concentration rose from 29.7 at.% to 33.1 at.% with increasing temperature, accompanied by an increase in nanocrystallite size from 2 nm to 15 nm and enhanced hardness from 13.51 GPa to 15.66 GPa. All nitrided layers exhibited significantly improved wear resistance relative to the unmodified steel. The layer nitrided at 450 °C demonstrated optimal performance due to a refined nanostructure and minor CrN that enhance plastic deformation resistance and facilitate oxide film formation. While, the 350 °C treated layer exhibits diminished thickness and reduced hardness, and the 550 °C treatment induces excessive CrN precipitation and micro-cracking, consequently compromising both toughness and wear resistance.

Surface nanocrystallization is a critical approach for improving mechanical and functional properties of materials. Beyond conventional mechanical routes, chemical loading presents a promising pathway for nanocrystallization via interstitial-driven phase transformation. However, the characteristics and mechanisms underlying chemical load-induced nanostructuring remain insufficiently elucidated. This work investigates the surface nanocrystallization of 17-4 PH martensitic stainless steel during low-temperature plasma nitriding at 350 °C. Microstructural characterization combining XRD, EPMA, and TEM revealed a nitrogen-saturated layer with a maximum hardness of 13.5 GPa. The modified layer consists of nanoscale domains formed via a diffusionless martensite-to-austenite transformation, as evidenced by broadened FCC peaks, dark-field images, and the absence of elemental partitioning in EDX maps. This process is driven by the cyclic accumulation of chemical and elastic-strain energy at the advancing nitrogen diffusion front, triggering a self-sustaining, periodic transformation. This study introduces a chemical-driven nanocrystallization mechanism for novel design of surface-nanostructured steels via controlled thermochemical processing.

This study aims to enhance the corrosion property of 17-4PH martensitic stainless steel, a material commonly used in industrial applications including nuclear power components, to enhance its performance in borate buffer solutions. The study employed plasma-based low-energy nitrogen ion implantation at temperatures ranging from 350 °C to 550 °C for 4 h to modify the steel surface. Microstructural characterization via XRD and TEM revealed the formation of a nanocrystalline nitrided layer, with thickness increasing from 11 to 27 μm and surface nitrogen concentration rising from 29.7 to 33.1% as temperature increased. Correspondingly, the nanocrystalline grains coarsened from an average size of 2 nm to 15 nm. The main findings showed that all nitrided layers significantly improved general corrosion resistance in pH 8.4 borate solution compared to the unmodified steel. An optimal performance with a corrosion potential of −169.4 mV(SCE) and a passive current density of 0.5 μA/cm2 was achieved at 450 °C, accompanying the development of a denser passive film with high polarization resistance and lower defect density. It is concluded that the high interstitial nitrogen concentration within the nanocrystalline γ′N accelerates passivation kinetics and enhances corrosion resistance, with the applied point defect model clarifying the underlying improvement mechanism.

Objective: This study was conducted to address the harsh working environment of agricultural machinery and improve the wear resistance of soil-contacting components such as rotary tiller blades, thereby extending their service life. Method: Plasma-cladding technology was employed to prepare an iron-based wear-resistant coating on the surface of rotary tiller blades. The following parameter combination was optimized using response surface methodology (RSM): a cladding current of 144A, a cladding speed of 23 mm/s, a powder feeding rate of 23 g/min, and a cladding distance of 12 mm. The microstructure morphology, phase composition, microhardness, and wear resistance of the wear-resistant cladding layer were investigated. Results: The results indicate that the interface of the cladding layer is clean and free from significant porosity or defects, exhibiting good metallurgical bonding with the substrate. The primary phases identified in the cladding layer include α-Fe, Cr7C3, Cr2Fe14C, and Cr-Ni-Fe-C solid solutions. The average hardness of the cladding layer is 1171 Hv0.5, approximately 2.9 times that of the substrate. In wet sand–rubber wheel wear tests under identical conditions, the weight loss of the cladding layer is only 1/21 that of 65Mn steel, with minimal wear morphology. Field trials showed that the wear of the cladding layer rotary tiller blade was reduced by 24.5% compared with the unclad blade. The presence of the cladding layer significantly protected the integrity of the cutting edge, ensuring the functionality of the rotary tiller blade in cutting and throwing soil; thus, its original appearance was maintained even after prolonged wear. The findings of this study can provide a valuable reference for the enhancement of wear resistance for other soil-contacting components.

Polyether ether ketone (PEEK) nanocomposite coatings with diverse dimensional carbon nano-fillers to achieve low friction and low wear of moving mechanical parts in severe application conditions were not the same as the bulk polymer nanocomposites due to their special manufacturing processes. Herein, the flame spray processes were utilized to fabricate the PEEK and carbon fibers/PEEK (CFs/PEEK) nanocomposite coatings with one-dimensional carbon nanofibers (CNFs), two-dimensional graphene nanosheets (GNSs) and three-dimensional graphite nanoparticles (GNPs) in contents of 1.0 and 5.0 wt.

Flame spraying polymer composite coatings is an effective method by which to improve the surface properties of metal parts. The use of self-lubricating fillers to reduce the friction and wear of polymer composite coatings is beneficial for expanding the applications of moving mechanical parts under harsh conditions. CF / PEEK composite coatings with graphite fillers at mass fractions of 1wt.%, 2wt.%, and 5wt.% were prepared on 17-4PH steel substrates using flame spraying technology. The effects of the graphite content on the cross-sectional morphology, porosity, crystallization behavior, thermal performance, surface hardness, tribological properties, and wear mechanism of the flame-sprayed CF / PEEK composite coatings were studied using SEM, XRD, FTIR, TGA, nanoindentation, and tribological tests. The results showed that the porosity of the composite coatings first decreased and then increased with increasing graphite filler content. The porosities of the flame-sprayed composite coatings with 2wt.% graphite fillers were the lowest at 2.13%, which is 23.9% lower than those of the CF / PEEK coatings. The high graphite filler content causes an increase in the porosity, owing to the poor stacking of the melted PEEK particles during flame spraying. Graphite fillers with 5wt.% content led to little thermal degradation of the PEEK in flame-sprayed composite coatings. The crystallinity of the composite coatings initially increased and then decreased as the graphite filler content increased. The graphite fillers had little effect on the thermal weight loss rate of the composite coatings but increased the initial decomposition temperature and the temperature corresponding to the maximum weight loss rate, thereby enhancing the thermal stability of the flame-sprayed composite coatings. Low-content graphite fillers promote the surface hardness of the flame-sprayed composite coatings. The surface hardness of the composite coatings with 2wt.% graphite fillers is the highest at 0.326 GPa, which is 9.86% higher than those of the CF / PEEK coatings. A graphite filler content of 5wt.% led to a decrease in surface hardness, owing to the high porosities of flame-sprayed composite coatings. The friction factor of the flame-sprayed composite coatings initially increased and then decreased with increasing graphite filler content. The high friction factor of the flame-sprayed composite coatings with low graphite filler content could be attributable to the high bearing capacities of the composite coatings with high surface hardness. The friction factor of the flame-sprayed composite coatings with 5wt.% graphite fillers were the lowest at 0.291. The lubrication effect of the graphite fillers and high porosity of the composite coatings resulted in a low friction factor. The specific wear rate of the flame-sprayed composite coating first decreased and then increased with an increasing graphite filler content. The specific wear rates of flame-sprayed composite coatings with 1wt.% graphite was the lowest at 0.84x10(-6) mm(3) / (Nm), which is 37.8% lower than that of the CF / PEEK coating. The lubrication effects of graphite fillers and the high surface hardness of the flame-sprayed composite coatings with graphite fillers at low contents were beneficial for achieving low specific wear rates. The fatigue wear and abrasive wear of the flame-sprayed composite coatings with 1wt.% and 2wt.% graphite fillers were reduced, and the wear resistances of the coatings were improved. However, the adhesive wear of the flame-sprayed composite coating with 5wt.% graphite fillers increased, showing more severe wear. Graphite and CF fillers were used to modify the flame-sprayed PEEK composite coatings. Hence, the flame-sprayed composite coatings exhibited significant improvements in their mechanical and tribological properties. Moreover, the wear resistance mechanisms of the flame-sprayed composite coatings are discussed. Therefore, flame-sprayed CF / PEEK composite coatings with graphite fillers exhibit engineering application potential for friction reduction and wear resistance.

The characterization of pore distribution homogeneity in heterogeneous medium is difficult due to the lack of quantitative description of homogeneity, and the degree of homogeneity is closely related to measurement method and observation scale. In this paper, a kind of quantitative ultrasonic characterization strategy based on fractal theory, which takes into account the principle of matching observation scale with acoustic beam size, is proposed. The ultrasonic signals containing information about heterogeneous seal coating are extracted through water-immersed ultrasonic pulse-echo reflection method to characterize pore distribution homogeneity. The fractal dimension D and multifractal spectral symmetry B are specifically used to parameterize pore distribution homogeneity of microscopic images within acoustic beam size. By establishing simulation models combined with experimental microscopic images, the effects of pore number and size distribution on ultrasonic attenuation coefficient alpha are analyzed. Furthermore, the relationships between attenuation coefficient and the above two fractal parameters are established to quantitatively characterize pore distribution homogeneity with porosity of 1 %similar to 6 % and scales ranging from several to tens of microns. Finally, correlation coefficient R and root mean square error RMSE of the attenuation coefficient varying with two fractal parameters at variable observation scales of 3 mm, 2 mm, 1 mm, and 0.5 mm are compared. It should be noticed that considering the principle of matching observation scale with the acoustic beam size is crucial for quantitative ultrasonic characterization of fractal-based pore distribution homogeneity in heterogeneous medium. And the observation scale should be equal to or larger than acoustic beam size, which is >= 2 mm, under the testing conditions in this research.

Purpose This paper aims to investigate the lubrication characteristics of siliconized graphite with a wavy-tilt-dam (WTD) pattern applied to the hydrodynamic face seals. Design/methodology/approach It focuses on two friction pairs, carbon graphite versus tungsten carbide (CG-TC) and siliconized graphite versus siliconized graphite (SG-SG), through a three-dimensional elastic hydrodynamic lubrication numerical model that integrates finite difference method and finite element method. The consequence of axial elastic deformation of sealing pair materials on film thickness, film pressure, cavitation and sealing performance for a WTD mechanical face seal under full working conditions of ΔP = 0.8, 5.3 and 15.8 MPa are analyzed theoretically. Findings The nuclear hydrodynamic WTD face seal generates a convergent gap and exhibits a dual-characteristic behavior of hydrodynamic and hydrostatic effects under various ΔP . Compared to the CG-TC, the SG-SG shows a lower minimum film thickness, decreasing by 3.9%, 17.3% and 35.1%. The flow leakage rate decreases by 47.8%, 52.1% and 75.4%. In addition, the film stiffness increases by 46.8%, 49.8% and 97.8%. Thus, the SG-SG better deals with the dynamic tracking problem, and the sealing performance is stable. The strength and hardness of siliconized graphite enhance WTD sealing performance and improve cavitation control in high-pressure applications. Originality/value The lubrication characteristics of the siliconized graphite with a WTD pattern could inform the future design of hydrodynamic shallow groove wavy seals in boiler feedwater engineering implements under high-pressure conditions for the nuclear power industry. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2024-0382/

The hydrodynamic face seal of the main coolant pump (MCP) of a nuclear power plant operates under hydrodynamic lubrication. At low idle speed, the seal faces may touch, transitioning the lubrication regime from hydrodynamic to mixed. A new equation for the film thickness on the coning face with a wavy-tilt-dam (WTD) is developed, applying the average Reynolds equation with the Jacobson-Floberg-Olsson (JFO) boundary and using a statistical asperity contact model. Surface roughness and coning influence the minimum film thickness, load-carrying capacity, and friction coefficient, determining the shift from mixed to hydrodynamic lubrication. Under Delta P = 0.8 MPa and 20 r/min, the no-coning WTD face seal remains noncontact at sigma = 0.1 mu m, while it makes contact at sigma = 0.56, 0.35, and 0.28 mu m. The WTD face seals with f(coning) = 1.0 mu m at all sigma are in contact. Smoother surfaces reduce the summit contact probability, promoting the seal face to lift off. Coning decreases the hydrodynamic effect, leading to lower h(min) and a higher chance of rough summit contact. A test rig is built, and the idling process is simulated 50 times, revealing a contact wear pattern at sigma = 0.1 mu m with f(coning) = 1.0 mu m, while no wear pattern is observed with low coning. The 0-0.3 mu m coning value and sigma = 0.1 mu m are appropriate for WTD face seals under mixed lubrication. This research provides a basis for the stable operation of hydrodynamic WTD face seals in MCP.

The surface morphology of cylindrical thrust pad has been proven to have an important influence on the lubrication performance about the water-lubricated thrust bearing of nuclear reactor coolant pump,in order to identify the lubrication influence of different radial position and depth of circumferential trapezoidal groove on the surface of cylindrical thrust pad.Based on the surface mesh of thrust pad,the surface texture deviation is considered,the surface texture of the cylindrical surface on the sector thrust pad and its circumferential trapezoidal grooves are constructed,and the simplified Reynolds equation is solved by finite difference method.The results show that the thickness of water film decreases with the increase of the depth of the circumferential trapezoidal groove on the thrust pad surface,when the pressure of water film increases,the temperature of water film increases slightly,axial stiffness and axial damping increase significantly,the lubrication performance of the thrust pad decreases when the pressure peak on the surface of the thrust pad is separated into two pressure peaks on the inner side and the outer side.Finally,compared with the different grooves,circumferential trapezoidal grooves fixed depth,as the radial position of groove moves from inside to outside,the minimum water film thickness decreases first and then increases,and the maximum water film pressure rises,falls and rises again,shows that the M-shaped change rule,the maximum water film temperature increases first and then decreases,and the axial stiffness and axial damping increases first and then decreases,when the depth of circumferential trapezoidal groove is less than 0.1 mm,the pressure peaks are not obviously separated and still have good lubrication performance,the lubrication performance does not change greatly when the depth of circumferential trapezoidal groove is greater than 0.3 mm.The minimum water film thickness decreases first and then increases with the change of the position of the circumferential trapezoidal groove of the thrust pad from the inside to the outside,and decreases by 0.41 times with the increase of the depth of the groove.The maximum water film temperature increases first and then decreases,and increases by only 1.5％with the increase of the groove depth,and increases by 0.5％with the increase of the groove depth.The power loss of water film lubrication increases first and then decreases,and increases by 1.45 times with the increase of groove depth.The average water film shear stress increases first and then decreases,and increases by 1.96 times with the increase of groove depth.The minimum water film shear stress decreases first and then increases,and the minimum negative pressure value of-0.045 MPa appears at the position where the depth of the circumferential groove is 0.1 mm and the radial width is 0.6 times of the pad width,and the absolute value of the minimum water film shear stress is less than ambient pressure of the medium 0.1 MPa is not prone to cavitation erosion.For the crown thrust pad,except axial stiffness and damping,the lubrication performance of the annular trapezoidal groove shows a downward trend,but a reasonable setting of the annular groove can significantly increase the axial liquid film stiffness while reducing the acceptable liquid film thickness,which has a good support for the stable operation of the nuclear reactor coolant pump rotor.At the same time,pay attention to control the negative pressure area of the water outlet side,so as to suppress the influence of cavitation erosion caused by negative cavitation pressure.When the groove is preferred,the cavitation pressure can be controlled at 10％of the standard atmospheric pressure,that is,a smaller negative pressure level-0.01-0 MPa.The above conclusions provide technical support for the surface topography design,high performance manufacturing and bench test of the water-lubricated thrust pad of the extended nuclear reactor coolant pump,and have a certain reference value for the reliability design and in-service operation of the nuclear reactor coolant pump on the surface trace limit of the thrust pad,and are helpful for the research on the influence of surface scratches and textures of other topographies on lubrication.

Anisotropic wetting on certain surfaces endowed with structural asymmetry or compositional gradients commonly impedes the directional adjustment of liquid transport. We report here that directional liquid transport (DLT) against the tilt direction of nanohair and in the reverse direction was achieved on tilted-nanohair arrays (TNAs) and tilted-Janusian-nanohair arrays (TJNAs), respectively. Janusian compositional asymmetry on the surface of TJNAs was created by plasma polymer deposition on structurally asymmetric TNAs previously fabricated by Faraday-cage-assisted plasma nanotexturing. The structurally asymmetric TNAs led to DLT against the tilting direction due to the asymmetric wetting under the capillary imbibition between tilted nanohairs and the preferential coalescence of liquid against the tilt direction. The Janusian compositional asymmetry of TJNAs changing the capillarity imbibition condition between tilted nanohairs resulted in the transition of the liquid spreading direction along the tilt direction. The spreading direction along and against the tilt direction is predicted through a comprehensive analysis of the structural and compositional asymmetries of the TNAs and TJNAs.

Porous radiative cooling polymers have drawn significant attention for passive daytime cooling due to their desirable cooling performance and easy scalability. Since optimal pore parameters (i.e., pore diameter and porosity) will enhance light scattering, polymethyl methacrylate (PMMA) powders are sintered to fabricate samples with different pore parameters by the one-step full-dry powder sintering method. These samples have a hierarchically porous structure with pore diameters <5.0 m. The most porous sample has 43% porosity, 0.964 reflectance in the 0.3-2.5 mu m wavelength range, and 0.967 emittance in 8-13 mu m wavelength range (which is the atmospheric window). The measured cooling temperature difference decreases when the porosity is low for hierarchically porous PMMA with similar pore size distribution. The high sub-ambient cooling temperature reduction provided by hierarchically porous PMMA with optimal pore parameters is due to high solar reflectance when illuminated by the sun. Similar cooling trends are evident when sunlight is simulated by a Xenon lamp and an optical filter. The powder-sintered hierarchically porous PMMA with optimal pore parameters can be an excellent radiative cooler for passive daytime cooling applications.

The mechanical properties of WC-Ni coatings by HVOF thermal spraying were comprehensively evaluated by indentation tests at a wide load range of 10_ 1-103 N, i.e. nano-, micro- and macro-indentations. The correlation between process parameters and coating microstructure and mechanical properties was characterized via particle deposition temperature. The coating microstructure changes in reduced porosity, enhanced WC phase decomposition and better splats flattening were correlated to the particle deposition temperature rising. A porosity divergence between coating surface and cross-section was found as a quantitative anisotropy indicator to coating intrinsic lamellar microstructure formed by the splats flattening and piling up. Considering the lamellar microstructure, indentation responses on coating surface and cross-section were compared for hardness and elastic modulus evaluation below 3 N. The surface hardness is higher than that of cross-section, and both increased correlatively to the particle deposition temperature rising except for the almost constant surface hardness below 1 N. An analogous particle temperature-dependent behavior was also manifested for the elastic modulus by nano-indentation below 1 N. Interestingly, the elastic modulus by coating surface micro-indentation at 30 N presented identical particle temperature dependence to that by coating cross-section nano-indentation, both consistently representing the overall coating elastic modulus change trend verified by non-destructive ultrasonic test. Indentation fracture toughness on coating surface under 1.96 kN and on coating cross-section under 49 N was comparatively evaluated, and the values had a reverse trend of dependence on the particle deposition temperature. The particle-deposition-temperature dependent mechanical properties were interpreted by the coating intra-splats and inter-splats defects reduction with enhanced carbide-metal bonding essentially determined by the melting state of the metal binder phase, providing an insight to utilize indentation tests for characterizing thermal spray coatings.

The impact damage evolution of thermally sprayed WC-Ni coatings was studied under 1-8000 impacts at a fixed load of 10 kN order. With increasing impact number, the accumulative damages of coatings evolve by in-sequence occurrence of WC spallation, coating cracking, and mixed coating/interface cracking accompanied with crack length and width growing. To comprehensively evaluate the coated component performance by observed accumulative damages as the failure criteria, a critical impact number N c with critical load L c is proposed for the onsets of different cracking features. The impact resistance is quantified, by N c ( L cc ) for onset of the coating cracking, and N c ( L cm ) for the mixed coating/interface cracking. A subclassification is identified as N c ( L cm1 ) and N c ( L cm2 ), respectively, for sequential occurrence of the isolated interface cracking and the propagated interface cracking of the penetrated from the coating surface. As the coating thickness is increased from 50 to 200 μm, the impact resistance under a load of 11.1 kN is correspondingly improved with N c ( L cc ) prolonged from 3000 to 4500, and N c ( L cm1 ) from 4500 to 5000. In particular, N c ( L cm2 ) is 6000 for the 50 μm coating, but no N c ( L cm2 ) failure for the 200 μm coating up to 8000 impacts. The impact stress field analysis reveals reduced amplitudes of cyclic surface tensile stress and interface shear stress for the thicker coating, together with the interface shear stress shifting from a tensile-compressive alternating mode to a monotonous tensile one. The impact resistance of coated components under repetitive impacts is interpreted on thermodynamics where the thicker coatings mitigate impact mechanical energy dissipation of plastic strain energy in both coating and steel substrate, and accommodate larger reversible elastic strain energy during the periodic loading-unloading of impact cycles.

A time-dependent hybrid plasma model composed of a zero-dimensional global model and a two-dimensional fluid model is proposed for simulation of plasma chemistry and transportation of plasma during Cr thin film deposition by deep oscillation magnetron sputtering (DOMS). The global model deals with plasma reactions in the ionization region near the target with discharge voltage and current waveforms as inputs. The temporal plasma characteristics calculated by the global model are utilized as a boundary condition for the two-dimensional fluid model to simulate high-density plasma transportation in the diffusion region through the entire macropulse period. The full momentum equation taking inertia force into consideration is applied for ion momentum conservation in the fluid model instead of using the drift-diffusion approximation, which ensures validity of the simulation for low-pressure plasmas. The deposition flux as well as the kinetic and potential energy fluxes transferred to the growing films are calculated by the hybrid model. Microstructure evolution of the DOMS deposited Cr thin films from zone I to zone T is attributed to the growing kinetic and potential energies as the charging voltage increases according to the structure zone diagram. The deposition rate loss in DOMS is explained by the back attraction effect, sputtering yield effect, and densification of the films.

Clean-integrity processing of nuclear-grade AISI 316L austenitic stainless steel components finished by the wire brush and sequent flap discs is performed for high-performance manufacturing of the nuclear power plant equipment. Two steel wire brushes of AISI 304 austenitic stainless steel and 65Mn carbon spring steel are used for the grinding under a spindle speed of 550-2000 rpm. Sequent polishing is carried out by the flap discs using silicon carbide cloth under 2000 rpm. An equivalent pitting corrosion resistance to that of the original stainless steel in 3.5% NaCl solution is obtained for finished samples by the combined processes. The contaminants composition of ground stainless steel samples is determined by the redness degree of chromaticity inspection. The contaminants microstructure and finishing-induced microstructure are dependent on the impedance phase angle change in eddy current impedance diagrams. The surface clean-integrity of nuclear-grade stainless steel is characterized by the series of nondestructive evaluation methods.

In plasma sprayed coatings, pores are the primary microstructure, and their features such as porosity, shape, and orientation significantly influence the thermal insulation and elastic properties of the coatings. Therefore, the ultrasonic characterization of pore feature parameters plays a crucial role in guiding the processing and predicting the lifespan of coatings. However, the coupling of multiple pore feature parameters leads to ill-posed problem and nonlinearity between these parameters and the ultrasonic feature signals, making it challenging to identify multiple pore feature parameters accurately. In this study, based on the "ultrasonic - elasticity - structure" interaction mechanism, a novel strategy for the ultrasonic quantitative identification of pore feature parameters and elastic constants in plasma sprayed coatings is proposed. Firstly, a random pore model (RPM) was developed to reveal the complex morphology of pores in plasma sprayed coatings. The porosity, average aspect ratio, orientation factor, and contour roughness factor were statistically analyzed for 15 sets of constructed RPMs, followed by ultrasonic finite element simulations. Then, a sensitivity matrix (SM) inversion method is developed for the "ultrasonic - elasticity" relationship by accurately measuring the elastic constants of the coatings through ultrasonic wave velocity inversion at multiple angles, yielding a relative error of only 0.57%. Lastly, a Multi-output Support Vector Regression machine learning model optimized by genetic algorithm (GA-MSVR) was proposed to establish the "elasticity - microstructure" relationship and identify multiple pore feature parameters based on elastic constants. The maximum relative errors for the four pore feature parameters are found to be 12.28%, 6.35%, 18.87%, and 7.62%, respectively, demonstrating the feasibility of the proposed strategy. Furthermore, the sensitivity matrix was employed to explain the cause for the larger relative error of the orientation factor. In summary, a challenging task of quantitatively identifying pore feature parameters in plasma sprayed coatings is addressed by proposing a novel solving strategy based on the "ultrasonic - elasticity - microstructure" interaction mechanism. The developed RPM, SM inversion method, and GA-MSVR model contribute to the accurate and comprehensive identification of pore feature parameters. The results obtained validate the feasibility of the proposed strategy.

The article presents the results concerning the cross-sectional energy density distribution of a pulsed ion beam for two types of diodes with electron open drift: with external magnetic insulation (250 kV, 80 ns, 0.6 T) and with self-magnetic insulation of electrons (250–300 kV, 120 ns, 0.8 T). Anode plasma is formed using a breakdown along the surface of the anode dielectric coating (single-pulse mode) or explosive electron emission (with double opposite-polarity pulses). It was found that, when the energy density of the ion beam exceeds ≈0.4 J/cm2, periodic spoke-type structures with a step of 3–6 cm in the beam cross section are formed. The processes of formation of such a structure—nonuniform density of anode plasma and self-organization of anode and/or cathode plasma in crossed electric and magnetic fields—are analyzed. It is shown that the formation of local plasma regions in the anode–cathode gap of an ion diode can cause the formation of a periodic structure of the cross-sectional energy density distribution.