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Considered are the prospects of applying complex post-processing for an additive manufactured product with the deposition of a multilayer composite coating [Ti0.2C0.8/a-C]40 at the final stage. It is shown that heat treatment, finish milling, ion-plasma nitriding and burnishing with a sliding diamond indenter of a PH1 steel part obtained by selective laser melting (SLM) before deposition of a thin-film coating provides the coating with a minimum surface roughness Ra = 82-86 nm and a maximum hardness of 25.2 ± 1.4 GPa with an increase in the microhardness of the entire “coating-substrate” system. © 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 express particular gratitude to A.G. Merkushev and I.Y. Malygina for their participation in the work.

[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 Lc 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%.

The structure and micromechanical properties of a 316L stainless steel produced by the selective laser melting (SLM) technique have been studied in its initial state and the following heat treatment: quenching from 1050 ºС and 4-hour annealing at 480 ºС. The heat treatment does not result in changing the steel phase composition, however, it reduces the microhardness by 5%, HM hardness (Martens hardness) by 12% and indentation hardness by 16% at HIT maximum load. The heat treatment also increases the Е* contact elasticity modulus by 14% due to the lower porosity of the material. As soon as heat treatment provides no strengthening of the steel synthesized by SLM, deformation processing, chemicothermal treatment and application of thin coatings may become quite promising strengthening methods. © 2020 Institute of Physics Publishing. All rights reserved. The main results were funded by the RFBR and Sverdlovsk Oblast, project number 20-48-660065. The results of the electron diffraction phase analysis were obtained by the M.N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences (IMP UB RAS) within the state assignment of Ministry of Science and Higher Education of the Russian Federation (theme “Structure” No. № АААА-А18-118020190116-6). The studies were performed at the collaborative access center “Testing center of nanotechnology and advanced materials” of IMP UB RAS.

Using transmission electron microscopy, Mossbauer spectroscopy, and measurements of hardness, the carbide precipitation during tempering of steel X153CrMoV12 containing (mass pct) 1.55C, 11.90Cr, 0.70V, and 0.86Mo is studied after three treatments: quenching at RT and deep cryogenic treatment, DCT, at 77 K or 123 K (−196 °C or −150 °C). In contrast to some previous studies, no fine carbide precipitation after long-time holding at cryogenic temperatures is detected. After quenching at room temperature, RT, the transient e(e′) carbide is precipitated between 373 K and 473 K (100 °C and 200 °C) and transformed to cementite starting from 573 K (300 °C). In case of DCT at 123 K (−150 °C), only fine cementite particles are detected after tempering at 373 K (200 °C) with their delayed coarsening at higher temperatures. Dissolution of cementite and precipitation of alloying element carbides proceed at 773 K (500 °C) after quenching at RT, although some undissolved cementite plates can also be observed. After DCT at 123 K (−150 °C), the transient e(e′) carbide is not precipitated during tempering, which is attributed to the intensive isothermal martensitic transformation accompanied by plastic deformation. In this case, cementite is the only carbide phase precipitated in the temperature range of 573 K to 773 K (300 °C to 500 °C). If DCT is carried out at 77 K (−196 °C), the e(e′) carbide is found after tempering at 373 K to 473 K (100 °C to 200 °C). Coarse cementite particles and the absence of alloying element carbides constitute a feature of steel subjected to DCT and tempering at 773 K (500 °C). As a result, a decreased secondary hardness is obtained in comparison with the steel quenched at RT. According to Mossbauer studies, the structure after DCT and tempering at 773 K (500 °C) is characterized by the decreased fraction of the retained austenite and clustering of alloying elements in the α solid solution. It is suggested that a competition between the strain-induced transformation of the retained austenite and carbide precipitation during the wear can control the life of steel tools.

The tool steel X220CrVMo 13-4 (DIN 1.2380) containing (mass%) 2.2C, 13Cr, 4V, 1Mo and the binary alloy Fe–2.03 mass% C were studied using transmission electron microscopy, Mossbauer spectroscopy, X-ray diffraction and internal friction with the aim of shedding light on processes occurring during deep cryogenic treatment. It is shown that the carbon atoms are essentially immobile at temperatures below −50 °C, whereas carbon clustering in the virgin martensite occurs during heating above this temperature. An increase in the density of dislocations, the capture of immobile carbon atoms by moving dislocations, the strain-induced partial dissolution of the carbide phase, and the abnormally low tetragonality of the virgin martensite are found and interpreted in terms of plastic deformation that occurs during martensitic transformation at low temperatures where the virgin martensite is sufficiently ductile.