N.N. Cherenda

Structural and phase composition changes in aluminium induced by carbon implantation

Abstract The results of Rutherford backscattering analysis, Auger electron spectroscopy, transmission electron microscopy and X-ray diffraction analysis of the surface aluminium layer after carbon implantation are presented in this work. The energy of implanted ions was 20 keV, the implantation dose varied in the range of 0.4–4.0×1017 ions/cm2. The growth of carbon implantation dose resulted in an increase of carbon concentration over the stoichiometric level. Phase composition analysis showed that carbon implantation led to the formation of a Al4C3 compound. The possible mechanism of carbide formation based on ion-induced crystallisation was proposed. The behaviour of stress induced by carbon implantation in the aluminium lattice was also discussed.

Nitriding of steel and titanium surface layers under the action of compression plasma flows

The elemental and phase compositions of St3 steel and VT1-0 titanium surface layers nitrided by the action of compression plasma flows (CPFs) have been investigated. The plasma flow parameters are shown to be correlated with the modified-layer nitrogen content. The basic mechanism by which the steel and titanium surface layers are saturated with nitrogen has been revealed. The performed experiments indicate that an increase in the absorbed energy density leads to a decrease in the nitrogen concentration because a shock-compressed layer is formed in the near-surface region, impeding nitrogen diffusion into the sample. The higher nitrogen concentration of surface layers treated by CPFs is achieved by increasing the pressure of the residual nitrogen atmosphere. It has been established that γN-Fe nitrous austenite, α″-Fe(N) and α′-Ti(N) martensitic phases, and γ′-Fe4N and δ-TiNx nitrides can be produced by nitriding the surface layers of St3 steel and VT1-0 titanium.

The effect of nitrogen implantation on the tribological properties of composite aluminium alloys

Abstract In this work the tribological properties of powder aluminium alloys (Al + Al 2 O 3 , Al + C) and cast aluminium were investigated after nitrogen implantation (energy 30 keV, implantation dose 2 × 10 17 ions cm −2 ). Phase analysis of the surface modified layer was conducted using X-ray diffraction. Auger electron spectroscopy measurements were also performed to obtain composition and depth profiles of the implanted layer. It was found that implantation led to an increase in the initial friction coefficient of the powder alloy Al + C and cast aluminium. The formation of the AlON phase in the surface layer took place during implantation, according to data of the phase and element composition analysis.

Erosion of materials under the effect of compression plasma flows

Erosion of the surface of St3-type steel and BrB2-type bronze samples as well as bronze and copper samples with zirconium coating under the effect of compression plasma flows is studied. The results show the increase in mass removed from the surface of samples with the growth of energy absorbed by the surface layer and with the growth of the number of pulses. Probable mechanisms of erosion have been discussed. Erosion leads to the decrease in the coating element concentration in the alloyed layer in the case of the coating/substrate system treatment. This effect depends on thermal characteristics of the treated material.

Modification of structure and mechanical properties of high-speed steel P18 at combined plasma and thermal treatment

The results of an investigation of the structure and microhardness of P18 high-speed steel under combined plasma and heat treatment are given. The layer modified by compression plasma flows is found to consist of two regions containing solid solutions based on bcc and fcc iron, these regions having cellular and lamellar structures. Subsequent annealing makes it possible to recover carbides dissolved under the effect of a plasma flow. Combined treatment yields formation of a more uniform and dispersed structure which cannot be obtained using conventional thermal treatment.

Formation of titanium nickelide surface alloy under impact of compressive plasma flows on the nickel-titanium system

Structural-phase states of surface layers of titanium alloyed with nickel are studied after impact of plasma compression flows (CPF) on titanium previously coated with nickel. It is shown that, at the thickness of nickel coating of 3–6 μm, action of CPF with energy density in the range from 9 to 23 J/cm2 provides formation of a surface layer containing titanium nickelide TiNi, Ti2Ni, and a solid solution based on high-temperature titanium phase β-Ti(Ni). It is found that the modified surface layer is characterized by a fairly low modulus of elasticity (48 GPa), which makes possible its usage as a biocompatible material.

Thermal Stability of the Structure and Phase Composition of Titanium Treated with Compression Plasma Flows

The results of studying the structure and phase composition of the surface layer of commercial pure VT1-0 titanium treated with compression plasma flows in nitrogen atmosphere and annealed in the temperature range of 400–900°C for 1 h are presented. Using the X-ray diffraction method, the α-Ti(O) solid solution is found to form in the titanium surface layer at 500°C, without pretreatment with plasma, and to transform into the titanium oxide TiO2 (rutile) phase at 600°C. Pretreatment of titanium with compression plasma flows promotes the formation of α-Ti(N) solid solution decreasing the rate of surface oxidation and increasing the initial temperature of rutile formation to 700°C, which indicates enhancement of the thermal stability of this structure.

Elemental composition of the surface layer of a heat-resistant nickel alloy doped with zirconium atoms under the action of compression plasma flows

The element distribution over the surface layer in a heat-resistant nickel alloy, which is doped with zirconium under the action of compression plasma flows generated by a compact magnetoplasma compressor, is investigated. An analysis is performed using the helium ion backscattering method (the ion energy is 6MeV) and energy-dispersive X-ray microanalysis. It is established that the doping element concentration decreases due to an increase in the absorbed-energy density and the number of pulses. The segregation of zirconium atoms is observed in the surface layer with a thickness determined by the conditions of the action. This process is related mainly to the formation of zirconium oxide (oxynitride).