V. P. Sergeev

Effect of the nanostructuring of a Cu substrate on the fracture of heat-resistant Si-Al-N coatings during uniaxial tension

The effect of the nanostructuring of the surface layers in a Cu substrate on the microstructure, mechanical properties, and fracture mechanisms of heat-resistant Si-Al-N coatings during uniaxial tension is studied. The nanostructuring of a substrate is performed by the following two methods: bombardment by Zr+ ion beams and ultrasonic impact treatment. Depending on the state of the substrate, different spallation mechanisms are found to operate in the Si-Al-N coatings during mechanical loading. The maximum shear strength of the coating/substrate interface is shown to be achieved due to ion bombardment of the substrate.

Study of crack resistance of TiAlN coatings by scratch testing

Scratch tests were performed to study failure mechanisms in TiAlN coatings deposited on substrates from steel 12Cr18Ni9Ti. It is shown that coating failure begins with crack generation at the apices of pile-ups formed along the scratch due to plastic ploughing of the substrate material. With further increase in indentation load the failure process is governed by the competition between tensile stresses behind the indenter arising due to friction force and stresses at the contact area periphery due to coating bending under normal load. Substrate pretreatment by Ti ion beams is shown to simultaneously increase the hardness and crack resistance of TiAlN coatings.

Structural modification of TiAlN coatings by preliminary Ti Ion bombardment of a steel substrate

The TiAlN coatings deposited onto steel 12Cr18Ni9Ti substrates before and after preliminary treatment by Ti ion beams are studied by X-ray diffraction, transmission electron microscopy, atomic force microscopy, and nanoindentation. The modification of the surface layer of a substrate is shown to change the structure and the preferred orientation of the coatings. The mechanical properties of the TiAlN coatings are found to depend substantially on the ion bombardment time.

Effect of the number of layers in Zr-Y-O/Si-Al-N multilayer coatings on their mechanical properties and wear resistance

The peculiarities of the wear of multilayer coatings comprised of crystalline Zr-Y-O and amorphous Si-Al-N layers during tribological tests under conditions of dry friction are investigated. It is shown that the simultaneous development of the abrasive and adhesive wear mechanisms gives rise to the extreme dependence of the wear resistance of specified coatings on the number of layers. The major factors that allow one to enhance the mechanical properties and wear resistance of the investigated coatings are discussed.

Elastic stresses and microstructure of TiAlN coatings

By X-ray diffraction and transmission diffraction electron microscopy methods, the phase composition, macro- and microstresses, and microstructure in a Ti1–xAlxN coating and a substrate were investigated. The coatings were deposited by magnetron sputtering of a Ti–Al target in an Ar + N gas reaction mixture on a substrate of austenitic steel 12Kh18N10T preliminarily bombarded with a titanium ion beam. It was found that the increase in the duration of the preliminary ion treatment of the substrate leads to increasing compression macrostresses and refining of a nanocrystalline columnar microstructure in the Ti1–xAlxN coating.

Increasing the fatigue life of 12Cr1MoV steel by surface nanostructuring with a Zr+ ion beam. Structure, properties, and fracture pattern

The paper presents the results of static and cyclic tensile tests and alternate cyclic bending tests of 12Cr1MoV specimens in the initial state and after surface nanostructuring with a Zr+ ion beam. Examination by optical and scanning electron microscopy and interference profilometry revealed differences in the formation of the deformation relief and in the character of cracking of the modified surface layer. The changes occurring in the modified surface layer were estimated by nanoindentation, X-ray analysis, and fractography. The nanostructure formed in the treated surface layer was analyzed by transmission electron microscopy. The difference in deformation is interpreted using the multiple cracking concept. The effect of substantial enhancement of fatigue strength is associated with retarded plastic deformation and fatigue crack propagation in the modified surface layer.

The effect of pretreatment by titanium ion beam on the internal stresses and microstructure of the TiAlN coating obtained by magnetron sputtering

The increase in duration of titanum ion pretreatment of the substrate-austenitic steel leads to a decrease in the transverse dimensions of the nanocrystalline columnar coating Ti1−xAlxN structure, emergence of ferritic layer between coating and substrate and an increase in the compressive macrostresses both in the coating and in the substrate.

Obtaining composite Zr-Al-O coating on the surface of zirconium by microplasma oxidation

The paper describes the application of the microplasma oxidation for production of Zr-Al-O composition on the surface of zirconium. Certification of a new-type power supply for depositing oxide ceramic coatings by microplasma oxidation was also carried out. The growth rate of Zr-Al-O coating amounted around 0.2 nm/s, which around 10 times exceeds that for depositing similar coatings using the similar equipment. We have studied the change of surface morphology and the chemical composition of the formed ceramic coating by means of EVO 50 scanning electron microscope and X-ray spectral analysis.

About structural phase state of coating based on zirconium oxide formed by microplasma oxidation method

The oxide-ceramic coating based of zirconium oxide is formed by the method of microplasma oxidation. The producing modes of the oxide layers on E110 zirconium alloy are under testing. It was found that using microplasma treatment of E110 zirconium in aluminosilicate electrolyte makes possible the formation of porous oxide-ceramic coatings based on zirconium alloyed by aluminum and niobium. The study is focused on the modes how to form heat-shielding coatings with controlled porosity and minimal amount of microcracks. The structural-phase state of the coating is studied by X-ray diffraction analysis and scanning electron microscopy (SEM). It was found that the ratio of the monoclinic and tetragonal phases changes with the change occurring in the coating formation modes.

Phase transformations of nanostructured Zr-Y-O coatings under loading

The deposition of nanostructured Zr-Y-O/Si-Al-N-based coatings was implemented by the pulse magnetron methods. The structural-phase state of the nanostructured coatings was studied with TEM and X-ray analysis. The phase transformation in Zr-Y-O layer was observed with the X-ray diffraction analysis in the “in-situ” mode under loading in conditions of free and constrained volumes. It was found, that there were martensitic phase transformations at certain deformation levels under the conditions of the free volume and martensitic phase transformations in the local regions of the coating layer with the structure fining in constrained volume.