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Coatings (WoS, Q2, IF=2.881), 2021, Volume 11, Issue 5, 532

Abstract. The study is devoted to the development and testing of technological principles for the manufacture of solid end mills from ceramics based on a powder composition of α-SiAlON, β-SiAlON, and TiN additives, including spark plasma sintering powder composition, diamond sharpening of sintered ceramic blanks for shaping the cutting part of mills and deposition of anti-friction Si-containing diamond-like carbon (DLC) coatings in the final stage. A rational relationship between the components of the powder composition at spark plasma sintering was established. The influence of optimum temperature, which is the most critical sintering parameter, on ceramic samples’ basic physical and mechanical properties was investigated. DLC coatings’ role in changing the surface properties of ceramics based on SiAlON, such as microrelief, friction coefficient, et cetera, was studied. A comparative analysis of the efficiency of two tool options, such as developed samples of experimental mills made of SiAlON/TiN and commercial samples ceramic mills based on SiAlON, doped with stabilizing additives containing Yb when processing nickel alloys (NiCr20TiAl alloy was used as an example). DLC coatings’ contribution to the quantitative indicators of the durability of ceramic mills and the surface quality of machined products made of nickel alloy is shown.

Keywords. Diamond-like carbon coating; high-speed milling; nickel alloy; SiAlON; spark plasma sintering; roughness; wear resistance.

Microstructure of ceramic specimens with DLC coatings: (a) SEM image of a thin section of an experimental specimen 80% (90α10β) + 20% TiN ceramics with DLC coating; (b) SEM image of a thin section of commercial ceramics specimen with DLC coating; (c) SEM image of the DLC coating surface structure; (d) TEM image of the a two-layer DLC coating structure; (e) SAED of the (CrAlSi)N sublayer; and (f) SAED of the functional DLC layer.

Исполнители: Grigoriev, SN; Volosova, MA; Fedorov, SV; Okunkova, AA; Pivkin, PM; Peretyagin, PY; Ershov, A

Дата публикации: 22-10-2021

Источник: https://www.mdpi.com/2079-6412/11/5/532

Metals (WoS, Q2, IF=2.351), 2021, Volume 11, Issue 9, 1392

Abstract. Coatings with thickness 40 to 150 μm were formed by plasma electrolytic oxidation (PEO) on the zirconium alloy Zr-1Nb (Zr-1% Nb) in the slurry electrolyte containing 9 g/L Na2SiO3 5H2O, 5 g/L Na(PH2O2) and 6 g/L submicron Y2O3 yttria powder during 60 min under the AC electrical mode at current densities 20; 30 and 40 A/dm2. The surface morphology, structure, composition, and corrosion-protective ability of the formed coatings have been analyzed. At PEO current density 30 A/dm2, a predominantly tetragonal phase of zirconia was formed in coatings. Increasing the PEO current density up to 40 A/dm2 promoted the formation of the coating surface layer containing submicron yttria particles. Electrochemical polarization studies in 0.5% LiOH solution showed that PEO coatings demonstrated high corrosion-protective ability. The dependence of the polarization currents on the PEO current density was found to be inconsequential.

Keywords. Plasma electrolytic oxidation; zirconium alloy Zr-1Nb; submicron yttria powder; PEO coating; surface morphology; structure; composition; corrosion-protective ability

SEM images in the mode of backscattered electrons of surface morphology: PEO coatings formed at current densities 20 (a), 30 (c), and 40 (d) A/dm2; submicron yttria particles on the surface of coatings formed at current densities 20 (b) and 40 A/dm2 (e,f).

Исполнители: Svetlana Savushkina, Mikhail Gerasimov, Andrey Apelfeld, Igor Suminov

Дата публикации: 22-10-2021

Источник: https://www.mdpi.com/2075-4701/11/9/1392

Wear (WoS, Q1, IF=3.892), Volumes 486–487, 204096

Abstract. The paper continues the investigation focused on various factors of wear of coatings deposited on metal-cutting tools. The paper presents the results of the investigation focused on the wear process typical for tools with the Ti-TiN-(Ti,Cr,Mo,Al)N multilayer nanostructured wear-resistant coating during the turning of steel. Particular attention has been paid to the study of the diffusion of iron (Fe) from the material being machined into the coating and of coating elements into the material being machined. It has been found that the diffusion of iron into the nanolayer structure of the coating is of periodic decaying pattern. Nanolayers of the coating with the high content of Cr-Mo exhibit the best barrier functions with respect to the diffusion of iron. The investigation has revealed the active oxidation of the layer of the material being machined in contact with the coating, with the noticeable formation of individual grains of iron oxide, which can have an abrasive effect on the coating surface. The studies have detected the diffusion of iron into the coating to a depth not exceeding 300–400 nm and the diffusion of coating elements (primarily, chromium) into the material being machined to a depth not exceeding 100 nm. The process of crack formation in the coating and the role of the crystalline structure and internanolayer interfaces in the inhibition of crack propagation have been investigated.

Keywords. Wear mechanisms; Cutting speed; Multilayer nanostructured wear-resistant coating; Diffusion; Crack formation; Influence of abrasive grain hardness

Wear diagram for the contact pads of the cutting tool (ISO 3685)

Исполнители: Sergey Grigoriev, Alexey Vereschaka, Filipp Milovich, Nikolay Andreev, Jury Bublikov, Nikolay Sitnikov, Catherine Sotova, Natalya Kutina

Дата публикации: 22-10-2021

Источник: https://www.sciencedirect.com/science/article/pii/S0043164821004804