Phase transformations in iron powders and their alloys due to shock wave treatment

The variation in the phase composition of metal powders and their alloys due to shock wave treatment has been examined, and the factors that promote the retention of high pressure phases under normal conditions are indicated. It is shown that shock wave conditions applied to a composite of metal and trinitrophenol produce an active carbon and nitrogen containing atmosphere that enables both carbides and nitrides to be synthesized.Far Eastern Polytechnic Institute, Vladivostok. Translated from Poroshkovaya Metallurgiya, No. 1 (361), pp. 88–91, January, 1993.     

Formation of chromium coatings alloyed with nickel on diamond

The methods of x-ray phase analysis are used to study the composition of chromium — nickel coatings and metallizing mixtures (metal spraying compositions) as a function of the annealing conditions. The thickness of the coatings is calculated from the weight gain by diamond. It is shown that coatings are formed mainly by the transfer of chromium and nickel through the gas phase to the reaction surface (diamond or the outer surface of the coatings) and diffusion of carbon from the diamond (into the coating) which determines the phase composition of the coating: Cr₃C₂, Cr, Cr₇C₃, and Ni. Nickel appears in the metal spraying compositions because of the reduction of NiO by the carbon of chromium and carbon monoxide. The formation of the phases in the metal spraying compositions, which block the intensity of evaporation of chromium (due to NiO restoration with chromium) and of Ni(Cr) (due to the dissolution of chromium in nickel), is the factor that limits the growth of the coating. This is the main reason for the decrease in the thickness of the coating when nickel monoxide is added to the chromium metallizing mixture.Institute of Materials Science Problems, Ukrainian Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, No. 1 (361), pp. 47–51, January, 1993.     

Diffusional metallization of graphite powders

Summary It was established that coatings can be formed on graphite in powders of the impregnating metal and its halide. Carbides are formed in the surface layer during the chromium, titanium, molybdenum, and tungsten impregnation of graphite. The growth of the coating layer thickness obeys a parabolic law.     

Elemental composition,topography, and wettability of the surface of graphite modified by ion-assisted deposition of chromium coatings

Elemental composition, roughness, and wettability of a graphite surface modified by ion-assisted deposition of a Cr coating ～300–1000 nm thick are investigated using the methods of Rutherford backscattering, atomic force microscopy, and contact angle measurements. It is established that, in addition to chromium, coatings involve hydrogen, carbon, and oxygen from residual gases of a vacuum chamber because of their incomplete pumping by vacuum pumps and 1–2 at % silicon diffusing from the graphite. It is determined that, as the coating thickness increases, the surface roughness of the modified graphite increases and becomes the predominant factor in increasing its hydrophobicity.