The wear resistance of highly porous titanium in the tribo-pair with bronze under boundary lubrication condition was investigated. According to analyses of worn surfaces of highly porous titanium, it was shown that the main reason of poor wear resistance were subsurface pores that led to nucleation of micro-cracks in the subsurface layer and thereby intensified fatigue (delamination) wear. For improvement of wear resistance of highly porous titanium, the surface engineering methods, such as deformation (ball burnishing, BB), diffusion (gas nitriding, GN), and their combination—deformation–diffusion treatment (DDT), were considered. It was shown that surface hardening of highly porous titanium by BB, GN, and DDT reduces the weight wear intensity and the friction coefficient of the tribo-pairs by 1.4, 3.5, 4.0 and 1.8, 2.3, 3.2 times, respectively. Such an improvement in the tribological properties of highly porous titanium after surface hardening is explained by changes in the main wear mechanism of the tribo-pairs from adhesive and fatigue to abrasive. The highest wear resistance of highly porous titanium was observed after surface deformation–diffusion treatment, as this treatment provides a combination of the positive effects of both ball burnishing (closing of surface pores) and nitriding (formation of a surface chemically inert and hard nitride layer).

The microhardness and abrasive wear resistance of cast Al-Si alloys after plasma-electrolytic oxidation (PEO) in a weakly alkaline basic electrolyte (3 g/L KOH + 2 g/L Na₂SiO₃), as well as with the addition of H₂O₂, were determined. X-ray analysis showed that the PEO layer comprises two oxide phases, namely α-Al₂O₃ and γ-Al₂O₃, as well as sillimanite -Al₂O₃ · SiO₂ and a small percentage of mullite -3 Al₂O₃ · 2SiO₂. Silicon is present in the structure of the oxide layer, and its percentage is greater than that of the alloys in their initial state. It has been shown that the characteristics of PEO layers on AK9 and AK12 silumins synthesized in an electrolyte of basic composition increase (microhardness up to 900–1000 HV and abrasive wear resistance by 14–57 times). The formation of PEO layers in the base electrolyte with the addition of 3 g/L of hydrogen peroxide intensifies the synthesis process and promotes the formation of high-temperature oxide phases (in particular, corundum). The abrasive wear resistance of both silumins with PEO layers synthesized in such an electrolyte increases by 30–70%.

The surface characteristics and friction behaviour of titanium Grade 2 with modified nitride (TiN, Ti₂N) and boride (TiB) compound layers were investigated. It was shown that during non-contact boriding in oxygen-containing medium of titanium, the diffusion processes take place mainly by the interscale mechanism; however, during nitriding, besides the traditional interscale diffusion mechanism, the grain boundary mechanism of diffusion of nitrogen atoms is also realized. The optimal set of surface roughness parameters (height and step parameters, a combination of kurtosis and asymmetry, and profile reference curve parameters) was obtained after boriding. It was determined that the intensity of the adhesive wear of the tribo-pairs with stainless steel and ultrahigh molecular weight polyethylene under dry sliding conditions was influenced not only by the hardness but also roughness of the modified surface layer. The lowest friction coefficient was fixed for the TiB compound layer in both tribo-pairs.

Based on the analysis of known methods of surface hardening of aluminum alloys (chromium plating, plasma electrolytic oxidation, hard anodizing), the prospects for pulsed hard anodizing are shown both for improving the functional characteristics of alloys and for large-scale implementation of this method. The purpose of this work is to show the possibility of pulsed hard anodizing to improve the serviceability of low-strength aluminum alloy 1011 under conditions of abrasive and sliding wear. The influence of the pulsed anodizing temperature on the phase-structural state of the synthesized layers, their abrasive wear resistance, and tribological characteristics in various lubricants were established, and the mechanism of wear of these layers was proposed. It is shown that with an increase in the temperature of pulsed anodizing, the wear resistance of the synthesized layers increases, and their abrasive wear resistance decreases. The negative effect of lubricating media on the wear resistance of the synthesized layers compared to tests under dry conditions was shown, and an explanation for this phenomenon is proposed. A significant (up to 40 times) increase in wear resistance in dry friction of anodized low-strength aluminum alloy 1011 compared to high-strength aluminum alloy 1050 was shown.

Aluminum (Al) components of high quality often require an optimal ratio of lightness and favorable mechanical properties. In order to improve the physical-mechanical properties of Al, an aluminum oxide (Al₂O₃) film is usually formed on the surface of Al, which itself is characterized by high strength, hardness, corrosion resistance, and other technical properties. Unfortunately, depending on the conditions, the oxide film may be formed from different crystal phases on the Al surface, which are not always of desirable quality, i.e., the α-Al₂O₃ phase. The present review demonstrates that the properties of the Al₂O₃ film may be improved by Al processing with a laser beam according to the scheme: Al (Al alloy) → electrochemical anodizing → treatment with laser irradiation → α-Al₂O₃. Both Al substrate and the anodizing electrolyte affect the phase transformation of anodic Al₂O₃. Laser irradiation of the Al₂O₃ surface leads to high heating and cooling rates, which may promote the formation of a highly crystalline α-Al₂O₃ phase on anodic Al₂O₃.

Oxide layers on the surface of the aluminum alloys D16 and AMg6 and on arc coatings sprayed with electrode wires made of the alloys D16 and AMg6 were synthesized using plasma electrolytic oxidation (PEO). The microstructure, phase composition and micro-hardness of the PEO layers were studied. In addition to the two main phases (α-Al₂O₃ and γ-Al₂O₃), a small amount of a metastable crystalized Al_2.427O_3.64 phase was found in their structure. A comparison was made of the wear resistance and friction coefficients of the synthesized PEO layers during friction tests in pairs with other PEO layers, a galvanic chromium coating, cast iron, steels and bronze of the BrC30 type. The results of the friction tests for the various PEO layers on aluminum alloys in tribo-contact with high-hardness elements made of hardened or chrome-plated steel justify the possibility of their use in a friction pair. We experimentally showed the influence of glycerin additive in motor oil 15W30 on the change in the friction coefficient of the PEO layers synthesized on the aluminum alloys and on the arc-sprayed coatings on their surfaces in tribocouples with hardened steel.