Three types of sintered alloys were fabricated based on cobalt, nickel and high-temperature alloy ZhS32-VI matrix with titanium carbide strengthening phase. TiC content was in a range of 30–50 vol. %. The melting temperatures of alloys are higher than 1320°C, and they may undergo undamaged through all technological procedures together with turbine blades, including soldering and outgassing. DSC analyses indicates no additional thermal effects until melting, which confirms their structural stability. The examinations of microstructure revealed three types of constituents – TiC particles, matrix solid solution and blow outs – structural defects having negative effects on all the studied properties. It was found that heat resistance of nickel based sintered alloys at the temperature of 1100°C is superior as compared with the alloys based on cobalt and alloy ZhS32-VI. It has been established that wear resistance in conditions of fretting wear at temperatures of 20, 850, 950 and 1050°C of sintered alloy with ZhS32-VI matrix is mostly superior as compared with the other alloys. The properties of produced alloys allow to use them for manufacturing of components of friction couples operating in conditions of high temperature fretting wear, including protective pads of turbine blades top shrouds contact faces.

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This study discusses the effect of a duplex aging + nitriding process on the wear resistance of an aged double-phase titanium alloy, BT22. Nitriding was applied simultaneously with the heat treatment of the alloy, which is advantageous over the conventional heat and surface treatment methods applied to titanium alloys. According to the results, the thickness of the case depth of the nitrided samples was 40–50 μm. Moreover, nitrogen was uniformly dispersed in the substrate, which was indicated by the hardness tests. The average microhardness of the substrate material was 300 HV0.01, while the hardness of the top layer was 1190 HV0.01, which is an almost four-fold increase. The applied duplex treatment substantially affected the wear performance of the tested alloy. For the untreated alloy, the maximum coefficient of friction was 0.8, while in the surface-modified sample, the maximum fluctuations reached 0.6. The abrasive wear process was dominant in the nitrided samples, while delamination and adhesive wear were observed for the untreated specimens. The nitrided alloy exhibited double the wear resistance of the untreated samples. The proposed treatment does not require additional time or energy consumption, providing a substantial technological advantage over conventional methods. Though the alpha case reduces the mechanical performance of titanium, the nitriding of only the component sections intended to withstand friction will have a positive effect.

The kinetics of nonfixed-abrasive wear of spark-deposited and laser-spark coatings on titanium alloy is studied. The coatings are deposited using electrode materials with different ZrB 2 contents. It is revealed that the wear rate of the coatings decreases with higher ZrB 2 content of the alloying electrode, after laser fusion, which increases the hardness of the outer layer, and with longer deposition of the coating, which increases its thickness It is shown that combined ZrB 2 -based coating can compete with spark-deposited WC + 3%Co coating.This paper continues the research [1] and focuses on the kinetics of the abrasive wear of ZrB 2 -containing coatings deposited with electrospark alloying (ESA) and combined laser-electrospark method. The ZrB 2 -containing electrode materials were developed at the Institute for Problems of Materials Science (National Academy of Sciences of Ukraine). Table 1 shows the numbers of the samples and compositions of the electrode materials.Tests for abrasive wear resistance were conducted in air with a NAUU friction machine ( Fig. 1) used to compare the wear resistance of materials and coatings during friction on a nonfixed abrasive. Our wear-resistance testing procedure corresponds to GOST 23.208-79 and is close to US standard ASTM G65-04. A 30 × 30 mm sample with a coating is pressed down with a rubber roll 50 mm in diameter, which rotates and supplies the abrasive to the contact area. The press-down force is controlled by loading. The tests were performed at a sliding speed of 0.163 m/sec and a load of 44.1 and 84.2 N. Quartz sand (SiO 2 ) with a grain size of 100-160 μm was used as an abrasive. The wear was measured gravimetrically to 0.0001 g. The volume wear was assessed taking into account the density of the material deposited. 436 3 4 5 6 2 1 Fig. 1. Friction machine with a nonfixed abrasive: 1) rubber roll, 2) sample, 3) feeder, 4) sand, 5) tray, 6) load Figure 2 shows the wear rate (I) of different ZrB 2 coatings on VT-20 alloy as a function of length (L) andtime (τ) of the process. The same dependences were obtained for VT-20 titanium alloy without coating (sample 1) and for spark-deposited WC + 3% Co coating (sample 2). The VK-3 electrode material is selected because the lowcobalt alloy has the highest abrasive wear resistance among WC-Co hard alloys [2]. The three-stage kinetic dependences I (L, τ) are typical of sliding friction [3] and show changes in polyoxide tribofilm in the 'abrasive particle-coating surface' contact area during abrasive wear. The first stage (L ≤ 100 m) is characterized by severe wear, in which a tribofilm forms. The uncoated VT-20 alloy has the highest surface wear rate at this stage, which is determined as tgα = I/L(τ). As the ZrB 2 volume content of the alloying electrode (Table 2) and of the coating increases, the wear rate decreases (Fig. 2). The L value, which corresponds to the 'severe wear → weak wear' transfer for the starting uncoated VT-20 alloy (~200 m) is twice as high for the coatings (~100 m); i.e., a tribofilm over the coatings f...