Page 45 - НАЦІОНАЛЬНА АКАДЕМІЯ НАУК УКРАЇНИ

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charges, as well as the parameters of the coating spraying process, on the formation of
the structure, phase composition and wear resistance of the coatings under conditions of
boundary lubrication during friction and abrasive wear were used as a guideline.
The process of creating hard anodised layers on aluminium alloys has been updated
by incorporating hydrogen peroxide (30-50 mg/l) into the electrolyte solution, which is
composed of 20% sulfuric acid. Another method involves the use of ozone gas during the
synthesis process. The use of this material has allowed for significant improvements in
several key areas. The thickness of the anodized layer has been increased by 50-60%,
microhardness has been boosted by 40-50%, abrasive wear resistance has been enhanced
by 15%, and wear resistance in a friction pair with a steel ball has been increased by 30%.
We have developed a method for pulsed hard anodising of aluminium alloys. This
method allows one phase or a mixture of two phases to form in the structure of the
anodised layer (depending on the electrolyte temperature (–5…+5)°C) during the
synthesis process. The Al₂O₃•H₂O (boehmite) phase in the microstructure of the
anodised layers provides high microhardness and abrasive wear resistance, while the
Al₂O₃•3H₂O (hibinite) phase provides high tribological properties. The anodised layer
obtained using the pulse method was 15–20% thicker and had 1.5–3 times greater wear
resistance than layers anodised using stationary synthesis, and 2.5–8 times greater wear
resistance than the D16 alloy.
It was shown that during the synthesis of PEO layers on top of thermal spray
coatings of the Al-Mg, Al-Ni, Al-Cu, Al-Ti systems, low-melting and fluid eutectics are
formed from mixtures of oxides (Al 2O 3 + MgO), (Al 2O 3 + NiO), (Al 2O 3 + CuO), (Al 2O 3
+ TiO 2), which fill discharge channels more easily than the refractory oxide Al 2O 3. This
made it possible to reduce the porosity of the synthesized PEO layer (from 8...10 to
3...5%), increase the corundum content in it (from 30 to 70%), increase its microhardness
(by 300...500 HV 0.3) and abrasive wear resistance (by 4...6 times). The wear mechanism
of different types of counterbodies (made of cast iron, bronze, babbitt and steel) during
their frictional interaction with the PEO layer was established. With a counterbodies
hardness of up to 300 HV 0.3, wear occurred due to the removal of the layer from the
counterbodied surface by protrusions on the PEO layer as cutters. Such a friction pair is
suitable for use only at specific loads up to 4 MPa. At a counterbody hardness of
(300…1000) HV 0.3, wear occurred due to multiple elastic or elastic-plastic deformation of
the counterbody surface. Such a friction pair is suitable for use at specific loads up to
10 MPa.
A method for supersonic arc spraying of wear-resistant restorative coatings from
cored wires (CW) of the Fe-Cr-Si-Mn-B-C alloying system was developed. A supersonic
air jet with a Mach number of 2 was obtained at the nozzle outlet. The air jet pressure
increased from 0.6 to 1.2 MPa, which was accompanied by a two-fold increase in its
velocity (from 300 to 600 m/s), and that of molten droplets by 60–90 m/s. As a result, the
coating hardness increased from 600 to 900 HV 0.3, abrasive wear resistance by 1.4–1.7
times, and the level of residual tensile stresses of the first kind in the coating decreased by
2 times.
Based on the CW of a Fe-Cr-Si-Mn-Ti-B-C alloying system, a CW for arc spraying
of wear-resistant coatings with an exothermic charge based on boron carbide, chromium,