4
M. V. Ved’ et al.
of the above techniques for deposition of thin film multicomponent systems is
the possibility to flexibly control the content of components, rate of deposition,
and surface condition through the variation of the composition of electrolytes
and regimes of polarization (static or pulse, reverse current, or a decrease in
potential) [18, 19]. Because of this it is possible to fabricate the deposits of varied
qualitative and quantitative composition and with desirable functional properties,
such as microhardness; wear-, thermo-, chemical, and corrosion resistance; catalytic
activity; etc. [20–22].
Most researchers note outstanding properties of synergistic metal alloys of the
iron triad with d4-elements. Thus, the results of studies [4, 8, 23] show that the FeW, Co-W, and Co-W-Fe alloys successfully compete with galvanic chromium on
wear and corrosion resistance. The hardness of the Co-W-Fe alloys with the content
of tungsten ≈30% by mass is close to the hardness of chromium coatings, while the
corrosion resistance is considerably higher. The Co-W coatings synthesized by the
authors of [24] demonstrate microhardness of 550 HV. The represented results [15]
demonstrate a considerable increase in the microhardness and corrosion resistance
of Co-Mo-W coatings in comparison with the material of the substrate. Of practical
interest are studies of the authors of [5, 6] on the electrosynthesis of the ternary
Fe-Mo-W alloys with improved physical, mechanical, and anticorrosion properties.
Improved electrocatalytic activity of the binary alloys Co-W was demonstrated for
the model reaction of the electrolytic hydrogen evolution [8], catalytic oxidation of
benzene [17], and catalytic methanol oxidation in acidic media [25].
It should be noted that most of the published results deal with the binary Fe(Ni,
Co)-Mo(W) alloys. More to the point, the main attention is paid to the composition
of electrolytes. The world scientific literature presents a significant number of
positive results of the multicomponent alloy deposition from the gluconate-chloride
[4], citrate and citrate-ammonia [23], pyrophosphate [26], and sulfate-citrate [27]
electrolytes by galvanostatic and nonstationary mode. However, the main problem
of the presented technologies remains the low content of refractory components and
current efficiency.
It is obvious that the formation of coatings in each individual case depends
first on the qualitative [28] and quantitative [29] composition of electrolyte. The
variation in the electrolyte component concentration is an effective tool for leveling
of the potential difference of alloying components, according to the theory of codeposition of several metals in the alloy [30]. Therefore, not only the concentrations
of alloying components and their ratios but also the content of the ligand in the
electrolyte, namely, the lack or excess of citrate ion concentration relative to the total
concentration of complexing agents, will affect the composition and morphology
and, consequently, the properties of the coatings.
Secondly, the composition of electrolytic deposits, the ratio of components,
and the phase composition of coatings are essentially affected by the synthesis
conditions [31]. In turn, the structure of alloy predetermines the properties and areas
of application of coatings.
M. V. Ved’ et al.
of the above techniques for deposition of thin film multicomponent systems is
the possibility to flexibly control the content of components, rate of deposition,
and surface condition through the variation of the composition of electrolytes
and regimes of polarization (static or pulse, reverse current, or a decrease in
potential) [18, 19]. Because of this it is possible to fabricate the deposits of varied
qualitative and quantitative composition and with desirable functional properties,
such as microhardness; wear-, thermo-, chemical, and corrosion resistance; catalytic
activity; etc. [20–22].
Most researchers note outstanding properties of synergistic metal alloys of the
iron triad with d4-elements. Thus, the results of studies [4, 8, 23] show that the FeW, Co-W, and Co-W-Fe alloys successfully compete with galvanic chromium on
wear and corrosion resistance. The hardness of the Co-W-Fe alloys with the content
of tungsten ≈30% by mass is close to the hardness of chromium coatings, while the
corrosion resistance is considerably higher. The Co-W coatings synthesized by the
authors of [24] demonstrate microhardness of 550 HV. The represented results [15]
demonstrate a considerable increase in the microhardness and corrosion resistance
of Co-Mo-W coatings in comparison with the material of the substrate. Of practical
interest are studies of the authors of [5, 6] on the electrosynthesis of the ternary
Fe-Mo-W alloys with improved physical, mechanical, and anticorrosion properties.
Improved electrocatalytic activity of the binary alloys Co-W was demonstrated for
the model reaction of the electrolytic hydrogen evolution [8], catalytic oxidation of
benzene [17], and catalytic methanol oxidation in acidic media [25].
It should be noted that most of the published results deal with the binary Fe(Ni,
Co)-Mo(W) alloys. More to the point, the main attention is paid to the composition
of electrolytes. The world scientific literature presents a significant number of
positive results of the multicomponent alloy deposition from the gluconate-chloride
[4], citrate and citrate-ammonia [23], pyrophosphate [26], and sulfate-citrate [27]
electrolytes by galvanostatic and nonstationary mode. However, the main problem
of the presented technologies remains the low content of refractory components and
current efficiency.
It is obvious that the formation of coatings in each individual case depends
first on the qualitative [28] and quantitative [29] composition of electrolyte. The
variation in the electrolyte component concentration is an effective tool for leveling
of the potential difference of alloying components, according to the theory of codeposition of several metals in the alloy [30]. Therefore, not only the concentrations
of alloying components and their ratios but also the content of the ligand in the
electrolyte, namely, the lack or excess of citrate ion concentration relative to the total
concentration of complexing agents, will affect the composition and morphology
and, consequently, the properties of the coatings.
Secondly, the composition of electrolytic deposits, the ratio of components,
and the phase composition of coatings are essentially affected by the synthesis
conditions [31]. In turn, the structure of alloy predetermines the properties and areas
of application of coatings.