Структурно-фазовые превращения в многослойных периодических композициях W-B4C с периодом 2,5 НМ при нагреве

Abstract

Heating-generated changes of the structure and phase composition of multilayers, consisting of alternating W and B4C layers with the bilayer thickness (period) of 2.5 nm, were studied by X-ray scattering and electron microscopy in the temperature range of 100 – 1000°С. Phase transformations were found to occur in the W-B4C multilayer coatings as follows: the tungsten carbides (most W3C) formed below 600°С, above 600°С the carbides were substituted by the W2B and WB borides, and at a temperature over 950°С WB4 and W2B5 appeared. These transformations were accompanied by volume changes: the thickness of B4C layers decreased, and the thickness of W-containing layers increased. The W-containing layer fraction in the period increased from 0,38 to 0,51 after 1000°С annealing. The period of the multilayers expanded by 1% after 600°С annealing, and it went back to its initial value at further heating. Destruction of the multilayer structure happened at 950 – 1000°С