A. Yu. Koval

The Effect of Compacting Rolling on the Properties of Titanium Powder Mill Products

The effect of deformation stress on the consolidating of titanium powder strips obtained by symmetrical and asymmetrical rolling is analyzed. It is determined, that the strength of green strips after asymmetrical rolling is substantially higher than that of conventional strips: for low and medium deformation stress (by a factor of 3–5) and for high deformation stress (by a factor of >10). The repeated rolling improves the mechanical properties of sintered strips. Titanium powder strips produced through optimal asymmetrical rolling possess better mechanical properties than conventional titanium strips.

Mechanical and Fatigue Properties of Powder Titanium Strips, Obtained by Asymmetric Rolling

The mechanical properties of titanium powder strips obtained by asymmetric rolling technique are investigated. It is found out that the use of asymmetric rolling during the consolidating and repeated compacting rolling allows obtaining a strip with better mechanical properties than that obtained by conventional technique. The fracture surface of a titanium strip obtained by symmetric rolling has a significant ratio of the interparticle fracture. After asymmetric rolling, the fracture surface is totally dimpled. It is shown that the asymmetric rolling improves the quality of interparticle contact and, consequently, the ductility and fatigue resistance increase significantly.

Interaction Between Components of the Copper-Based Self-Lubricating Antifriction Composite at 900 and 950°C

It is shown that a self-lubricating antifriction composite with microheterogeneous structure is synthesized during sintering of the Cu–Ni–P–MoS2 powder in hydrogen at 900 and 950°C. The structure of the self-lubricating antifriction composite formed at 900°C represents an α-solid solution of nickel in copper hardened by complex phosphide MoNiP, in which sulfide Cu2Mo3S4 is distributed. Molybdenum disulfide interacts with hydrogen at 950°C to form Cu2S and MoP. The structure of the self-lubricating antifriction composite formed at 950°C differs from the previous one in the amount of α-solid solution of nickel in copper, type (MoP) and content of hardening phase in it, and type (Cu2Mo3S4 and Cu2S) and amount of antifriction structural component.

Structural changes in friction surfaces of plasma-sprayed coatings

The features surface morphology are considered for plasma-sprayed coatings used with various counterbodies under conditions of boundary friction. The tribotechnical characteristics of the coatings are examined in relation to the structure. There is found to be a substantial effect from the porosity on the formation of the secondary structures, the changes in topography, and the changes in elemental composition of the friction surface.

Variation of the phase composition and strength characteristics of a tungsten-free hard alloy in the early stage of oxidation

The mechanical properties of a tungsten-free cemented carbide subjected to thermal oxidation in air have been found to be fairly dependent on the isothermal holding time. The strength parameters of the material are affected by the oxidation of the materials and the higher Ni content in the metal-binder. That increase is due to the decomposition of the Ni3Mo intermetallic phase during heat treatment of the cemented carbide in air.

Structural changes in eutectic alloys during flame spraying

Results of studying microstructural changes in eutectic alloys with different types of spraying are summarized. A distinctive feature of alloys which have eutectic carbides of the type MeC is that they do not change their shape and composition during different methods of spraying. The morphological characteristics of oxides phases are demonstrated. Addition of alloying elements with an affinity for oxygen makes it possible to alter the morphological characteristics.