This article presents the results of the ball-on-disk wear test (ASTM G99) and linearly reciprocating ball-on-flat sliding wear test (ASTM G133) for molybdenum disulfide–based coatings in a wide ...range of operating conditions. Monocomponent suspension coatings based on molybdenum disulfide and doped with graphite, ceramics, and polytetrafluoroethylene are studied in a vacuum, at elevated temperatures, and under normal atmospheric conditions. The friction coefficient and service life of the coatings are determined depending on the application technology and operating conditions. The structure and chemical composition of the coatings and the mechanisms of coating wear and destruction are studied.
Ni50.7Ti49.3 alloy of coarse grained (CG) and ultrafine grained (UFG) microstructures were subjected to tensile tests at different strain rates of 10−1 s−1, 10−2 s−1, 10−3 s−1 and temperatures of ...25 °C, 50 °C and 200 °C. The CG state was attained by quenching and the UFG state by electroplastic rolling (EPR). Transmission electron microscopy of the UFG Ni50.7Ti49.3 alloy revealed the presence of shear bands and sub-grains. The microstructure after tensile testing revealed the presence of grains and twin planes of the B19′ martensite phase, which indicates that twinning also plays a role in the deformation of the alloy, in addition to crystallographic slip. The effects of grain size, strain rate and temperature on the stress-induced martensite transformation present during the tensile tests are discussed. Serrated flow was observed intermittently in the stress-strain curves of both CG and UFG Ni50.7Ti49.3 alloy for some specific combinations of strain rate and temperature. Serrations observed were not limited to the stress plateau region, which is typically seen in the stress-strain curves of NiTi alloys as a result of phase transformation, but were noticed rather randomly through the entire strain range. This unsteady flow behaviour is also discussed.
•The effect of temperature and strain rate on the SIM transformation in Nitinol has been established.•Suppression of SIM at the highest strain rate and temperature was more prominently observed in CG NiTi compared to UFG NiTi.•TEM analysis revealed the possible roll of twinning in addition to slip in the deformation of Nitinol.
An experimental study investigating the influence of macro-, micro- and nanoscale structural refinement and contact temperatures in the range of 20−800 °C on the tribological characteristics of shape ...memory Ti
49.3
Ni
50.7
alloy processed via severe rolling with a pulse current and subsequent annealing at various temperatures is presented. Analysis revealed an increase in alloy strength characteristics, a decrease in the adhesive component of the friction coefficient and a decrease in the tendency to seizure in the course of friction with a decrease in grain size. The temperature dependence of the adhesive component of the friction coefficient for all structure states was found to have a maximum at 250–350 °C.
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An in-depth analysis of calorimetric and volumetric data for direct, reverse, and deformation martensitic transformations in the nanostructured alloy Ti
49.3
Ni
50.7
with shape memory is carried ...out. The samples are obtained by cold rolling with the simultaneous action of a high-density pulsed current. A new technique for processing calorimetry spectra is applied, with the help of which, for the first time, the staging and kinetics of changes in the heat content are studied in detail, as well as thermal effects (enthalpy of individual stages) during direct and reverse martensitic transformations occurring under the influence of temperature. By processing volumetric data, using theoretical values of the dislocation density and elements of classical dislocation theory, it is shown that in the Ti
49.3
Ni
50.7
alloy with shape memory subjected to cold plane deformation (rolling) accompanied by the action of a pulsed current, a strain-induced martensitic transformation occurs. This transformation results in a positive volume effect (∆
V
/
V
≈ 3 × 10
–3
), which can be largely due to dislocations. It is demonstrated that the possible contributions of dislocations to the enthalpy of direct and reverse martensitic transformations in the Ti
49.3
Ni
50.7
alloy can and should be significantly lower in absolute value, but opposite in sign relative to the observed enthalpy of direct and reverse martensitic transformations in this alloy.
The ultrasonic dispersion and spark plasma sintering technique have been used to process Al2O3/Graphene nanocomposite (Al2O3/G) with 0-2wt.% graphene. The topography of fracture, microstructure, ...density, microhardness, Young modulus, electrical and thermal conductivity of Al2O3/G nanocomposite are investigated.
In the present work, the properties of Al
2
O
3
nanocomposite prepared via spark-plasma sintering and reinforced with 0.5–2 wt % graphene are studied. Samples with different graphene contents are ...subjected to measurements of density, microhardness, coefficient of friction of composite–ruby, and frictional wear rate of composite. The fracture and wear track surface are inspected via fractography, and the composite as a whole is examined via X-ray diffraction. The graphene additive is established to increase the microhardness and to decrease the frictional wear rate by two orders of magnitude on account of absence of flaking of grains.
The results of experimental studies of the effect of grinding structure, the con-tact temperature and the load on the tribological characteristics of the alloy with shape memory Ti49,7Ni50,3 obtained ...by rolling with a pulse current and subsequent annealing at different temperatures.
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