1 Nanostructured Functional Coatings of Iron Family Metals with Refractory. . .
19
Fig. 1.13 X-ray diffraction patterns for alloy Fe-Co-W deposited from electrolyte Mo9 at i = 2.5
A/dm 2
of pulse electrolysis favors changes in refractory metal content, and surface
morphology with micro-globular surface and crystalline-amorphous structure of FeCo-Mo deposits differs by crystallite size of the amorphous part of 7 nm that is
associated with nano-sized materials.
1.1.3 CoMoZr Alloy
Increasing the current density amplitude i by 2–4 A·dm −2 rises the molybdenum
content in the deposit Co-Mo-Zr up to ω(Mo) = 24 at.% (Fig. 1.14a) reaching the
concentration plateau at 24–25 at.% at current densities of 4–8 A/dm 2 . Coating
enrichment by this alloying component with increasing current density is entirely
predictable since the reduction of molybdate is at least a complex multistep process
including chemical reduction of intermediate molybdenum oxides with hydrogen
ad-atoms H ad [36, 42]. As we see from (Fig. 1.14b), the potential of the cathode
at electrodeposition of the coatings Co-Mo-Zr is in the range –(2.0–2.8) V. Thus
with increasing current density, electrode potential shifts in the negative direction
resulting in faster parallel reaction of hydrogen reduction to form H ad which are
involved in a chemical step of intermediate molybdenum oxide reduction. Due to
these processes, the Mo content in the deposits is increased. However, at current
densities above 8 A/dm 2 , reaction of hydrogen evolution becomes dominant as
evidenced by the current efficiency (Fig. 1.14b) whereby the molybdenum content
in the alloy decreases.
The dependence of the Zr content in the ternary coatings from current amplitude i
has an extreme character with a maximum ω(Zr) = 3.6–3.7 at.% at current densities
of 4 A/dm 2 (Fig. 1.14a). It should be stated that when the amplitude of the current is
19
Fig. 1.13 X-ray diffraction patterns for alloy Fe-Co-W deposited from electrolyte Mo9 at i = 2.5
A/dm 2
of pulse electrolysis favors changes in refractory metal content, and surface
morphology with micro-globular surface and crystalline-amorphous structure of FeCo-Mo deposits differs by crystallite size of the amorphous part of 7 nm that is
associated with nano-sized materials.
1.1.3 CoMoZr Alloy
Increasing the current density amplitude i by 2–4 A·dm −2 rises the molybdenum
content in the deposit Co-Mo-Zr up to ω(Mo) = 24 at.% (Fig. 1.14a) reaching the
concentration plateau at 24–25 at.% at current densities of 4–8 A/dm 2 . Coating
enrichment by this alloying component with increasing current density is entirely
predictable since the reduction of molybdate is at least a complex multistep process
including chemical reduction of intermediate molybdenum oxides with hydrogen
ad-atoms H ad [36, 42]. As we see from (Fig. 1.14b), the potential of the cathode
at electrodeposition of the coatings Co-Mo-Zr is in the range –(2.0–2.8) V. Thus
with increasing current density, electrode potential shifts in the negative direction
resulting in faster parallel reaction of hydrogen reduction to form H ad which are
involved in a chemical step of intermediate molybdenum oxide reduction. Due to
these processes, the Mo content in the deposits is increased. However, at current
densities above 8 A/dm 2 , reaction of hydrogen evolution becomes dominant as
evidenced by the current efficiency (Fig. 1.14b) whereby the molybdenum content
in the alloy decreases.
The dependence of the Zr content in the ternary coatings from current amplitude i
has an extreme character with a maximum ω(Zr) = 3.6–3.7 at.% at current densities
of 4 A/dm 2 (Fig. 1.14a). It should be stated that when the amplitude of the current is