Two boride layers were found to form at the interface of iiron-chromiium alllloys (10 and 25% Cr) or an industrial 13% Cr steel and boron at 850-950 oC and reaction times in the range 1-12 h. In the case of a Fe-10% Cr alloy and the steel, the layers are based on the FeB and Fe2B compounds. With a Fe-25% Cr alloy, the constituent phases are FeB and CrB for the outer layer and Fe2B and Cr2B for the inner layer. Both layers are characterized by a pronounced texture. Diffusional growth kinetics of boride layers are close to parabolic and can alternatively be described by a system of two non-linear differential equations, producing a good fit to the experimental data. The temperature dependence of the layer growth-rate constants obeys a relation of the Arrhenius type.

Two boride layers based on the FeB and Fe 2 B compounds are formed at the interface between an Fe-15Cr alloy and boron at 850-950uC and reaction times up to 12 h, with the average chromium content being around 8 at-% in the former and 12 at-% in the latter. Both boride layers reveal a pronounced texture. Diffusional growth kinetics of the layers are close to parabolic and can alternatively be described by a system of two non-linear differential equations. Microhardness values are 17?4 GPa for the FeB layer, 14?4 GPa for the Fe 2 B layer and 0?95 GPa for the Fe-15Cr alloy base. The dry abrasive wear resistance of borided alloy samples is around 45 times greater than that of non-borided ones.

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The Gibbs free energies, enthalpies and entropies of formation of bismuth selenide Bi 2 Se 3 between 308 and 408 K, bismuth telluride Bi 2 Te 3 between 308 and 413 K, and their solid solutions between 670 and 840 K are measured using the e.m.f. method. Positive deviations of the activities of components in the solid solutions from the ideal behavior are found. The possibility of ordering effects in the solid solutions at lower temperatures is assumed.