Effect of the technological conditions of frictional treatment on the structure, phase composition and hardening of metastable austenitic steel

The process parameters of the frictional treatment (indenter material, medium, load) of the 12Kh18N10T chromium-nickel austenitic steel have been optimized for the criteria of strain hardening and the quality of the surface being treated. The paper studies effect of the multiplicity of the frictional action of a synthetic diamond indenter at room temperature in an argon medium and the loading temperature ranging between -196°C and +250°C on the hardening, phase composition and fine structure of the surface layer of the steel. It has been found that the completeness of the strain-induced γ→α′ martensitic transformation in the surface layer of the steel is strongly dependent on the multiplicity and temperature of loading and that the level of hardening rises with the multiplicity of action, but shows little dependence on the temperature of frictional treatment. © 2016 Author(s).Russian Foundation for Basic Research, RFBR: 15-08-0794701201354598Ural Branch, Russian Academy of Sciences, UB RAS: 15-9-12-45The work was done in the framework of the Complex Program of UB RAS (project No. 15-9-12-45) and the government assignment for IES UB RAS, theme No. 01201354598 supported by RFBR, project No. 15-08-07947

A new method of low-temperature cementation of stainless steel by decomposition of C2H2 in low-energy electron beam generated plasma

The method of low-temperature (400-500?C) cementation of AISI430 stainless steel by decomposition of acetylene in a wide (100 cm2) low-energy (200-300 eV) electron beam generated plasma in an Ar+C2H2 gas mixture was investigated. The composition of a beam Ar+C2H2-plasma is investigated and it is shown that the degree of decomposition of acetylene varies with the current and energy of the electron beam. It is shown that the magnitude of the flow of acetylene significantly affects the formation rate and hardness of the hardened layer. From the obtained results it can be seen that at fixed values of argon pressure ( ∼ 0.8 mTorr), beam current (3.5 A), bias voltage (-120 V), sample temperature (500?C) and exposure time (3 h) increase in QC2H2 from 1 to 4-5 cm3•min-1 leads to an increase in the thickness and microhardness of the hardened layer. With a further increase in QC2H2, an abrupt decrease in the rate of formation of the hard layer occurs. © 2019 IOP Publishing Ltd. All rights reserved.Russian Foundation for Basic Research, RFBR: 18-38-00561_mol_аThe authors thanks to A.I. Medvedev for X-ray phase analysis of samples and Yu.S. Surkov for the optical emission spectroscopy researches. The work was financially supported in part by the RFBR (grant No. 18-38-00561_mol_а)

Increasing the micromechanical and tribological characteristics of an austenitic steel by surface deformation processing

Frictional treatment (FT) with a sliding indenter forms highly dispersed (nano- and submicrocrystalline) austenitic structures with a hardness of 720 HV 0.025 in the surface layer of the 03Cr16Ni14Mo3Ti austenitic strain-resistant steel. According to the data on microindentation, FT increases the strength and of the surface layer of the austenitic steel and its resistance to elastic and plastic deformation. A high effectiveness of FT in the improvement of the tribological properties of the steel is demonstrated; namely, wear resistance increases 4 times under conditions of boundary friction as compared to the undeformed state. This is due to reduced plastic edging on the nanostructured surface. © 2018 Author(s)

Plasma Enhanced High-Rate Deposition of Advanced Film Materials by Metal Reactive Evaporation in Organosilicon Vapors

Dense homogeneous nanocomposite TiSiCN coatings with a thickness of up to 15 microns and a hardness of up to 42 GPa were obtained by the method of reactive titanium evaporation in a hollow cathode arc discharge in an Ar + C2H2 + N2-gas mixture with the addition of hexamethyldisilazane (HMDS). An analysis of the plasma composition showed that this method allowed for a wide range of changes in the activation degree of all components of the gas mixture, providing a high (up to 20 mA/cm2) ion current density. It is possible to widely change the chemical composition, microstructure, deposition rate, and properties of coatings obtained by this method, by changing the pressure, composition, and activation degree of the vapor–gas mixture. An increase in the fluxes of C2H2, N2, HMDS, and discharge current leads to an increase in the rate of coating formation. However, the optimal coatings from the point of view of microhardness were obtained at a low discharge current of 10 A and relatively low contents of C2H2 (1 sccm) and HMDS (0.3 g/h), exceeding which leads to a decrease in the hardness of the films and the deterioration of their quality, which can be explained by the excessive ionic exposure and the non-optimal chemical composition of the coatings. © 2023 by the authors.Russian Science Foundation, RSF: 20-79-10059This research was funded by the Russian Science Fund, grant number 20-79-10059

Obtaining of TiSiCN Coatings by Anodic Evaporation of Titanium and Decomposition of Hexamethyldisilazane in a Low-Pressure Arc Discharge

The method of TiSiCN-coatings deposition by anodic evaporation of Ti and decomposition of an organosilicon precursor (hexamethyldisilazane) in a low-pressure (∼1 mTorr) nitrogen-argon arc discharge with a self-heated hollow cathode is investigated. The plasma composition was analyzed by optical emission spectroscopy. TiSiCN coatings with a thickness of up to 10 microns and a hardness of up to 30 GPa were obtained in 1.5 hours at a temperature of 400 C. © Published under licence by IOP Publishing Ltd.The work was supported by the Russian Science Foundation (grant no. 20-79-10059)

Investigation of the Plasma Composition of a Discharge with a Self-Heating Hollow Cathode and an Active Anode in a Gas Mixture with Titanium and Hexamethyldisilazane Vapors

The analysis of composition of low-pressure (~0.1-1 mTorr) hollow cathode arc plasma in Ar+N2 gas mixture with Ti+hexamethyldisilazane vapors was carried out by optical emission spectroscopy. The influence of HMDS flow rate (1-10 g/h), discharge current (10-50 A) and Ti-vapors flow on hexamethyldisilazane decomposition degree and plasma composition and was investigated. The proposed plasma activation method provides both an intense flow and a high activation degree of metal vapors, and a sufficient decomposition degree of precursor vapors for the formation of solid TiSiCN coatings at a high deposition rate. Test coatings with a thickness of 6 microns and a hardness of 31 GPa were obtained in 1 hour at 400ºС. © 2021 Institute of Physics Publishing. All rights reserved.The work was supported by the Russian Science Foundation (grant no. 20-79-10059)

Effect of frictional treatment with a dense cubic boron nitride indenter on the micromechanical properties of the NiCrBSi-Cr3C2coating

Coatings based on NiCrBSi alloys with Cr3C2 addition can effectively resist wear, corrosion, and oxidation at high temperatures. The use of frictional treatment by sliding indenters as finishing is a modern way to create high surface quality and to enhance the strength and wear resistance of the surface of parts. The article studies the characteristics determined by instrumented microindentation of the surface of a NiCrBSi-Cr3C2 laser clad coating subjected to frictional treatments with a sliding indenter made of dense cubic boron nitride DBN in the air at loads on the indenter of 350, 500 and 700 N, and after grinding. Frictional treatment in the entire considered range of loads contributes to an increase in strength performance, as well as parameters indicating an increased ability of the coating surface to resist elastoplastic deformation. The highest growth of the parameters is observed after frictional treatment at a load of 700 N. © Published under licence by IOP Publishing Ltd

Features of frictional treatment of the composite NiCrBSi-Cr3 C2 laser clad coating

The authors conducted a comparative analysis of the effectiveness of frictional treatment with a sliding indenter of a NiCrBSi coating and a composite coating formed by laser cladding of a powder mixture of 85 wt.% NiCrBSi and 15 wt.% Cr3 C2 . The criteria were intensive strain hardening, favorable compressive stresses, and low surface roughness. Frictional treatment with an indenter made of cubic boron nitride at a load of 350 N provides less intense deformational hardening of the NiCrBSi-Cr3 C2 coating (microhardness growth from 900 to 940 HV 0.025) than the NiCrBSi coating (from 570 to 850 HV 0.025). This is due to the significantly higher initial hardness of the composite coating, because its structure, in addition to the phases characteristic of the NiCrBSi coating, contains large primary Cr3 C2 carbides, which did not dissolve during cladding, as well as elongated Cr23 C6 carbides, precipitated during cooling from a solid solution supersaturated with chromium as a result of the partial dissolution of Cr3 C2 carbides during cladding. Frictional treatment also results in a lower level of compressive residual stresses (−250 MPa) on the composite coating surface than on the NiCrBSi coating surface (−390 MPa). In contrast to frictional treatment of the NiCrBSi coating, when a smoothed surface with a nano-roughness is formed (Ra = 60 nm), frictional treatment of the composite coating forms a surface with a higher roughness (Ra = 310 nm) due to the creation on the surface of supporting “island frame” of large Cr3 C2 chromium carbides protruding 2 – 5 μm. © 2020, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.The work was performed with the financial support of the Grant from the President of the Russian Federation for young scientists MK-391.2019.8 and at the expense of funds making up the income from the trust management of the target capital for the development of UrFU, formed with the participation of UMMC-Holding Corp, as well as within the state order for IES UB RAS (AAAA-A18-118020790147-4) and IMP UB RAS (AAAA-A18-118020190116-6 and АААА-А19-119070490049-8). The experimental research was performed on the equipment of the Plastometriya Collective Use Center of IES UB RAS

The Influence of Frictional Treatment and Low-Temperature Plasma Carburizing on the Structure and Phase Composition of Metastable Austenitic Steel

Abstract: The features of the structure and phase composition of corrosion-resistant austenitic chromium–nickel steel (16.80 wt % Cr, 8.44 wt % Ni) subjected to carburizing in electron beam plasma at temperatures of 350 and 500°C, frictional treatment with a sliding indenter, and a combination of frictional treatment and plasma carburizing have been considered. It has been established that plasma carburizing results in the formation of a modified surface layer consisting of carbon-saturated austenite and carbides (Cr23C6, Fe3C); in this case, the formation of γC-phase occurs only at a temperature of 350°C. The depth of a modified layer increases with an increase in the carburizing temperature. It has been shown that it is useful to perform combined frictional treatment and plasma carburizing at a carburizing temperature of 350°C, since in this case the deformation-induced structure formed as a result of frictional treatment is preserved, and the precipitated carbides remain highly dispersed. In this case, frictional treatment should provide the formation of the deepest possible diffusion-active layer with a dispersed structure. © 2023, The Author(s).Ural Branch, Russian Academy of Sciences, UB RASElectron scanning microscopy was performed at the Plastometriya Center of the Collaborative Access at the Institute of Engineering Science, Ural Branch, Russian Academy of Sciences

Adhesion Strength of Ti1-xCx – DLC Multilayer Nanocomposite Thin Films Coated by Ion-Plasma Deposition on Martensitic Stainless Steel Produced by Selective Laser Melting Followed by Plasma-Nitriding and Burnishing

[Ti0.2C0.8/a-C]40 multilayer thin films composed of forty pairs of TiC and pure carbon layers were formed on a selective laser melted (SLM) martensitic stainless steel by means of ion-plasma deposition process. SLM steel was pre-treated by one of the two following schemes: (1) oil quenching from 1040°C followed by heating to 480°C for 4 hours and air cooling (HT), finish milling (FM); (2) HT, FM, ion-plasma nitriding followed by burnishing. Mechanical failure mode and critical load LС for damaging the coatings were determined using linear scratch tests performed at linearly-increased normal force. Indentation by conical diamond tip were carried out in order to asses an elastic recovery and energy dissipation coefficient defined as the ratio of plastic to total deformation energy. The scratch test results showed that the post-processing of the substrate strongly influenced the failure mode of the coating and increased the critical load from 320 mN to 920 mN. Indentation revealed that nitriding and burnishing before coating deposition increase the elastic recovery of the [Ti0.2C0.8/a-C]40 coating-substrate system from 24% to 68%. The energy dissipation coefficient drops from 79% to 45%. © 2021 Institute of Physics Publishing. All rights reserved.The research was funded by RFBR for Basic Research and Sverdlovsk Oblast (project No. 20-48-660065) and partially carried out within the state assignment for IMP UB RAS, theme “Structure” No. AAAA-A18-118020190116-6. The authors are grateful to A G Merkushev for his participation in the preparation of the part