RESEARCH OF THE MECHANISM OF COMPACTION OF MIXTURES OF POWDERS OF REFRACTORY CARBIDES WITH A METALLIC BOND IN EXPLOSIVE PRESSING ON A METAL SUBSTRATE

The results of investigations of the features of the behavior of the components of mixtures of refractory carbide powders with metals during explosive pressing are presented. It is shown that the main factor determining the compaction of mixtures is the dynamic flow of one of the phase components of the mixture into the initial pores of the powder. As the phase component of the mixture, the movement of which limits the degree of compaction and leads to the formation of a continuous matrix in the structure of the material pressed by the explosion, both the metal binder and the carbide component of the material can act.

Operation influence on structural and phase condition of 0.12C-1Cr-1Mo-1V-Fe steel

By the method of transmission electron diffraction microscopy the study of 0.12C-1Cr-1Mo-1V-Fe steel samples subjected to various long-term operation was conducted: 1) on the unfinished sample, 2) after prolonged operation without sample destruction, and 3) after prolonged operation brought to sample destruction. For each sample the phase composition was determined and the change in morphology of the structure was studied. It is established that operation of steel leads, firstly, to the destruction of plate pearlite and intensive ferrite fragmentation, secondly, to the redistribution of carbide component and, thirdly, to elastic distortion of the crystal lattice.

THE FEATURES OF DETONATION SPRAYING TECHNOLOGY FOR TUNGSTEN CARBIDE BASED COATINGS

The authors studied the effect of key parameters of detonation spraying process on tungsten carbidebased coatings and their mechanical properties, microstructure, and phase composition. Two main tasks are solved when developing the technology for spraying the carbide-containing materials. The relationship is established between the phase composition of tungsten-based coatings and their strength, hardness, and substrate adhesion. It was established that the WC dissolution in the metal phase promotes the increase of substrate adhesion as well as strength and hardness of coating material. A procedure of spraying coatings in the reduction mode is proposed: i.e., using working gas mixtures with excess acetylene. It prevents the decarbonization of WC carbides under the action of detonation products and environment. The phase composition heterogeneity (both along with the layer thickness and along the spraying spot diameter) is established. This depends on a complex of factors that determine the intensity of heat removal from the area of layer formation. For optimizing the structure and the mechanical characteristics of the coating, we need to control decarbonization of carbide component (WC) and formation of Ni (W) solid solution at different stages of spraying. Even a minor departure from carbon content leads to either appearance of graphite or formation of the fragile phase (Co3W3C), thus strongly reducing the mechanical properties.

XPS STUDIES OF THE STABILITY OF A ZIRCONIUM CARBIDE FILM IN THE PRESENCE OF ZIRCONIUM OXIDE AND HYDROGEN

X-ray photoelectron spectroscopy (XPS) has been used to study the interfacial chemistries of a 65-Å film prepared by depositing zirconium in an oxidizing environment onto a methane-pretreated 11-Å thick zirconium oxide film, which initially was deposited onto a gold substrate. The second metal deposition results in an outermost region composed of a mixed zirconium oxide, while below there is metallic zirconium followed by zirconium carbide and carbon on top of the first zirconium oxide film, which is itself in contact with the gold. The carbide component showed no changes on heating to 425°C, on treating with a hydrogen plasma at room temperature, or on heating the resulting film to 425°C. The oxide layers do show characteristic changes, and this also contrasts with earlier observations for a zirconium sulphide film. The zirconium carbide Zr3d 5/2 component has a binding energy of 180.6 eV.