Maksim Antonov

Assessment of cermets performance in erosive media

Ceramicmetal composites are a success story from the viewpoint of their many applications. However, the lack of design criteria and predictive models for durable applications of cermets poses a significant barrier to their wider application. The main objective of this paper is to review the cermets behaviour in tribological environment for better understanding material performance and durability in erosive media. For this reasons, microstructure of multiphase materials, features of structure development during sintering, fracture mechanisms, interface phenomenon, ability of energy dissipation and thermo-mechanical parameters were analysed with reference to WC-, TiC-, and Cr3C2-based cermets.

Some views on the erosion?corrosion response of bulk chromium carbide based cermets

Chromium carbide/nickel based composites are applicable in many environments involving tribo-corrosion due to their combined ability to resist wear and corrosion. Hence, they are candidate materials for use either in bulk as surface coatings in crude oil (offshore) or in power and marine industries. The aim of this work was to study the effect of material parameters such as composition and surface roughness, together with test conditions such as abrasive particle concentration, applied potential, temperature and time of experiment on the performance of chromium carbide based cermets. Potentiodynamic and potentiostatic tests were carried out as part of this work. SEM studies were also conducted to establish the mechanisms of the material degradation processes. Finally, erosion-corrosion maps were constructed based on the results. Material wastage, synergy and regime maps were developed for these materials and demonstrated that the performance of the cermet depends on the interplay of material and process variables.

The experimental and theoretical investigations of damage development and distribution in double-forged tungsten under plasma irradiation-initiated extreme heat loads

Abstract The influence of extreme heat loads, as produced by a multiple pulses of non-homogeneous fl ow of slow plasma (0.1-1 keV) and fast ions (100 keV), on double-forged tungsten (DFW) was investigated. For generation of deuterium plasma and fast deuterons, plasma-focus devices PF-12 and PF-1000 are used. Depending on devices and conditions, the power flux density of plasma varied in a range of 107-1010 W/cm2 with pulse duration of 50-100 ns. Power flux density of fast ions was 1010-1012 W/cm2 at the pulse duration of 10-50 ns. To achieve the combined effect of different kind of plasmas, the samples were later irradiated with hydrogen plasma (105 W/cm2, 0.25 ms) by a QSPA Kh-50 plasma generator. Surface modification was analysed by scanning electron microscopy (SEM) and microroughness measurements. For estimation of damages in the bulk of material, an electrical conductivity method was used. Investigations showed that irradiation of DFW with multiple plasma pulses generated a mesh of micro- and macrocracks due to high heat load. A comparison with single forged tungsten (W) and tungsten doped with 1% lanthanum-oxide (WL10) reveals the better crack-resistance of DFW. Also, sizes of cells formed between the cracks on the DFW’s surface were larger than in cases of W or WL10. Measurements of electrical conductivity indicated a layer of decreased conductivity, which reached up to 500 μm. It depended mainly on values of power flux density of fast ions, but not on the number of pulses. Thus, it may be concluded that bulk defects (weakening bonds between grains and crystals, dislocations, point-defects) were generated due to mechanical shock wave, which was generated by the fast ions flux. Damages and erosion of materials under different combined radiation conditions have also been discussed.

Hybrid Syntactic Foams of Metal – Fly Ash Cenosphere – Clay

This paper addresses an innovative syntactic foam produced out of metal powder (Fe), fly ash cenospheres (CS) and clay ceramic syntactic foams composite material (CM). Due to the low density of CS (bulk density - 0.38 g/cm3), the average density of these foams is about 2.6-2.9 g/cm3. It was found that CS undergoes phase transformation during thermal treatment at a temperature of 1200°C. Microstructural observations reveal a uniform distribution of CS and Fe particles in the composite. Compressive strength, and friction coefficient of obtained Fe/CS CM are in the range between 149 - 344 MPa and 0.15 - 1.1, respectively. Dependence of compressive strength on firing temperature is demonstrated exhibiting the maximum at 344 MPa; however, dependence of coefficient of friction on a material properties, obtained at different firing temperature exhibits the minimum value of 0.15 at the firing temperature of 1150 °C. The obtained syntactic form was shown to be a candidate for wear resistant applications.

Influence of Cr, Ti and Zr Oxides Formation on High Temperature Sliding of NiAl-Based Plasma Spray Coatings

In this study, the tribological characteristics of plasma thermal spray coatings are studied with particular interest on formation and performance of Cr, Ti and Zr oxides under dry sliding at 500 °С with Pin-On-Disc configuration against NiAl. Plain Cr2O3, TiO2 and ZrO2 coatings were tested to trace the difference between performance of original and in-situ formed oxides. Friction surfaces were examined using SEM and X-ray spectral analyses. The highest wear resistance of NiAl-CrB2 composite coatings can be related to the formation of Cr2O3 during the tribosynthesis process.

The Rolling Contact Fatigue of PVD Coated Spur Gears

The aim of the study was to investigate the resistance to rolling contact fatigue of a C:H:W and MoS2/Ti coated gears. The investigation of rolling contact fatigue was realised by means of a gear test rig using FZG PT C/10/90 pitting test. Four material combinations of gears were tested: wheel and pinion uncoated, wheel and pinion coated, wheel coated and pinion uncoated as well as wheel uncoated and pinion coated. The tests were performed using for lubrication mineral gear oil of API GL-5 performance level and 80W/90 viscosity grade. The results indicate that for the coated/coated pair (pinion and wheel coated) and coated pinion/steel wheel pair a significant decrease in the fatigue life compared to the uncoated gears was obtained. The best results were obtained in the case of the uncoated pinion / a-C:H:W coated wheel – even fourfold increase in the fatigue life was observed. This shows a very high potential of application of PVD coatings for gears.

High-temperature erosion of Fe-based coatings reinforced with cermet particles

High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbide–cobalt (WC–Co) and titanium carbide–nickel molybdenum (TiC–NiMo) cermet particles, are compared under high-temperature abrasive–erosive wear conditions. Both WC–Co and TiC–NiMo particles underwent fracture, as well as dissolution, during the spraying process, but in the case of WC–Co particles this process was remarkably less intensive. Under the low impact angle conditions, the WC–Co particle-reinforced coating exhibited 1.1 times lower wear than the TiC–NiMo particle-reinforced coating because of the larger amount of the reinforcement remaining. Under the normal impact angle conditions, the WC–Co particle-reinforced coating showed 1.2 times lower wear than the TiC–NiMo particle-reinforced coating because of the resulting larger size of the WC–Co reinforcement and a more ductile matrix.

Effect of Oxidation on Sliding Wear Behavior of NiCrSiB-TiB2 Plasma Sprayed Coatings

The main goal of this work is to study dry sliding wear behavior of NiCrSiB-TiB2 plasma sprayed coating against NiCrSiB coating. NiCrSiB-based powders with 10, 20, 40 wt.% TiB2 particles content were deposited on steel substrates by plasma spraying. The structure of NiCrSiB-TiB2 coatings consists of Ni-based matrix and TiB2 and CrB grains. Among the coatings studied, the NiCrSiB-20wt.%TiB2 shows excellent wear-resistance. The worn surfaces were observed using scanning electron microscopy and Auger electron spectroscopy to determine the wear mechanisms.

Assessment of the reliability of hardfacings for soil rippers

The results of a laboratory investigation (chemical composition, microstructure, hardness, wear rate), field testing of the welded overlays of the manual arc, and an assessment of the feasibility of coated soil rippers have been presented in the current work. Hadfield manganese steel (plain or alloyed by Cr, Ni, Mo, Si, B, or Cu) has been investigated with or without the addition of coarse-grained WC. Three commercially available overlays have been tested for comparison. Hadfield steel’s work hardening and high resistance to wear were observed during laboratory testing, while the results of field testing indicate that a significant work-hardening effect is not achieved in hard loamy soil. The lowest wear rate of soil rippers tested in loamy soil is enabled by overlays based on nickel with coarse-grained tungsten carbide particles (380 mm3 ha−1) or brazed hardmetal elements (350 mm3 ha−1).

Electrochemical Behaviour of TiCN and TiAlN Gradient Coatings Prepared by Lateral Rotating Cathode Arc PVD Technology

TiCN and TiAlN gradient coatings were deposited on the AISI 316L stainless steel substrates by lateral rotating cathode arc (LARC) physical vapour deposition (PVD) technology. Corrosion and tribocorrosion behaviour was studied in 3.5 wt. % NaCl solution. The thickness of coatings was about 3 μm. For both coatings the corrosion potential shifted to more positive values as compared to the uncoated substrate. The corrosion current density decreased for TiCN and TiAlN coatings indicating up to 40 folds higher polarization resistance. The coefficient of friction value of TiCN coating is three times lower and durability is six times higher than that of TiAlN coating under the same tribocorrosion conditions.