Theoretical and experimental investigation of the process of plastic deformation of sintered composite materials IV. Technological basis for controlling the state of the elements of the“hard” phase during deformation

Conclusions A relationship has been established between the level of compressive stress necessary for the commencement of simultaneous deformation of the dissimilar phases of a composite material on the one hand and, on the other, the magnitude of the jump in strength properties at the interfaces between these phases and the geometry of shape of thehard inclusions (parameter l/d). The feasibility is shown of predicting the behavior of thehard inclusions during the deformation of a composite material by analysis of the stressed state attained under any given conditions of plastic working. The basic principles have been determined of devising a technological process for the production of composite materials of fibrous structure from sintered blanks.Translated from Poroshkovaya Metallurgiya, No. 11(299), pp. 38–42, November, 1987.     

Densification and structure formation in the sintering of composite materials based on nitrides of the IV–V group transition metals. III. Sintering of composite materials in the (VN, TaN)—Cr systems

An investigation was made of densification and structure formation in composite materials in the systems (VN, TaN)—Cr during sintering in argon. It was shown that the shrinkage of these materials during liquidphase sintering is insufficient to provide dense composites (residual porosity was 35–40%). This is attributed to the low thermodynamic stability of VN and TaN, and the rapid evolution from these of nitrogen which accumulates in closed pores. Processes of heterodiffusion and alloy formation also have a negative effect on densification. Exchange reactions between chromium and the nitride-forming metals lead to the formation of a large quantities of intermetallics which embrittle the composite materials. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 13–18, January–February, 1999.     

Riction properties of composite materials of the system TiN - Ain. II. Effect of oxide films on friction and wear of a ceramic material — Steel system

Friction and wear are studied for materials of the system TiN — AlN preliminary oxidized at 800–1100°C. It was established that thin oxide films containing Al₂TiO₅ and α-Al₂O₃, that promote a decrease in frictional wear, form on the surface of composite materials of the system TiN — AlN. Our assumptions are confirmed that the improvement in tribological properties of TiN — AlN composites is caused by forming oxide screening layers that prevent direct contact between the ceramics and steel counter-body. At high rates (V=16 m/sec) and pressure (P=2.0 MPa) the oxide films form more rapidly. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(411), pp. 121–124, January–February, 2000.