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The paper examines how the structure and phase composition of Ti-Al-B alloys evolve at various consolidation stages in the composite powder mechanochemical synthesis and subsequent sintering under pressure. Two powder alloys with different boron content are studied. The amount of aluminum in both initial powder mixtures is the same and corresponds to TiAl. The content of boron is selected so as to form an aluminide matrix with 10 and 25 vol.% borides. It is established that phases form in the mechanochemical synthesis in the following sequence: Ti + Al → Ti (Al) → TiAl 3 and Ti 3 Al → TiAl. Titanium borides are formed simultaneously with TiO 2 and TiAl or after them, which confirms that these processes are interrelated. The mechanochemical synthesis for hours in a planetary-ball mill results in the formation of micron particles that have agglomerated or conglomerated (sometimes layered) composite structures. X-ray analysis is used to study the phase evolution of Ti-Al-and Ti-Al-B alloys. It is shown that the presence of boron in mechanical alloying reduces the degree of amorphization and promotes the formation of fine crystalline structure. In addition, the presence of boron prevents the formation of metal oxides and a number of intermetallides. It is established that the sintered dispersion-hardened Ti-Al-B material consists of an aluminide matrix with micron and submicron inclusions of borides. The increase in boron content leads to a higher amount of boride inclusions. As a result, the distance between them decreases and thus microhardness increases.

621.793We have studied phase formation in detonation coatings sprayed from Ti − 50 at.% Al powders. The powders of the alloy were obtained by various methods: crushing an ingot and mechanical alloying of Ti and Al. Using polyphase nanostructural materials activated by mechanical alloying makes the process of phase formation in the gas-thermal sprayed coatings based on them more general-purpose and controlled due to the more active and more subtle reaction of the material with the gaseous atmosphere.We have shown that from mechanically alloyed Ti − 50 at.% Al powder, using the detonation-gas spraying method we can consolidate a coating based on Al 2 TiO 5 by oxidizing action of the working gas on the powder and also a coating based on titanium aluminides with TiN inclusions by nitriding action.The phase composition of the cast microstructural γ-TiAl powder is inherited by the coating.

The paper examines the phase formation of detonation coatings sprayed from mechanically alloyed . It is shown that coatings with different phase compositions and functional properties can be consolidated from this activated powder by varying process conditions (including gas composition during detonation spraying). Three types of composite coatings with different structures are obtained: TiB and TiB 2 inclusions are distributed in an intermetallic matrix (Al 3 Ti, γ-TiAl); inclusions of oxides and oxynitrides are additionally present in the same structure; inclusions of borides, Al, and Ti are distributed in a mixture of intermetallic and nitride (TiN, AlN) phases.

621.793Operation of coatings based on tialite, γ-TiAl, titanium aluminides with discrete inclusions of TiN and also alloys based on cobalt, nickel, and titanium in friction pairs with polyethylene grade "Chirulen" and stainless steel 12Kh18N10T is studied. It is established that tialite coatings formed from nanostructure powders of Ti − Al by detonation deposition are the best for operation under dry friction conditions in a pair with stainless steel 12Kh18N10T (minimum friction coefficient and minimum wear of the contact surfaces). It is shown that in the sliding rate range selected effective operation of material in friction pairs with polymer is provided due to transfer it to the contact surface and formation between rubbing surfaces of a thin film fulfilling the function of a solid lubricant. It is established that stable operation with the minimum wear in a friction pair with polyethylene grade "Chirulen" is provided by a coating of γ-TiAl and Al 2 TiO 5 , and also coatings based on titanium aluminide with fine TiN inclusions.

A comparative microstructural analysis of the scale formed on the NiAl-Re detonation coating shows that the mechanism of its high-temperature oxidation can be changed with preliminary magnetic abrasive treatment (MAT). The scale formed over the NiAl-Re coating in ordinary conditions includes several layers (NiO-NiAl 2 O 4 -Al 2 O 3 ), while the scale formed on the MAT coating consists of an Al 2 O 3 monolayer with spinel inclusions. The differences in the oxidation of the NiAl and NiAl-Re coatings after MAT are attributed to changes in their dislocation structure.

The tribotechnical characteristics of dry friction against different materials are compared. It is established that nitrides and oxides present in the coatings improve the friction characteristics. It is found out that friction pairs containing similar metals have the highest seizure capability. The coating whose structure represents an intermetallic matrix with inclusions of solid phases as titanium borides and oxides has the best characteristics.

The paper examines the abrasive wear resistance of composite detonation coatings with different structures based on Ti-Al-B, Ti-Al-B-O, and Ti-Al-B-N systems. It is established that the coating consisting of an intermetallic matrix and solid-phase inclusions as titanium borides and oxides has the highest characteristics. The coating whose microstructure is based on a random two-phase mixture of relatively soft intermetallic and nitride phases and whose hard component is represented only by borides has the lowest wear resistance.