CONTACT INTERACTION OF ZIRCONIUM DIBORIDE WITH NICKEL AND ITS ALLOYS. І. THE PECULIARITIES OF CONTACT INTERACTION IN THE ZrB₂–Ni SYSTEM

Abstract

The interaction in the ZrB₂–Ni system with a change in the ZrB₂ content from 3.5 to 75 wt.% has been studied. It is shown that the process occurs through the contact melting mechanism, leading to the formation of a liquid phase, wetting the substrate with a contact angle of about 50°, even at 1250 °C. The liquid phase interacts with the substrate and crystallizes with time as more refractory compounds are formed. The structure and phase composition of the reaction products are determined by the ratio of the alloy components, representing double, triple, and more complex compounds based on the crystalline lattices of Zr–Ni intermetallides. The eutectic point is found at 13% ZrB₂ in the alloy. The eutectic nature of the ZrB₂–Ni quasibinary phase diagram limits the upper temperature application range for the alloys and associated materials in friction joints of fuel equipment. Considering that they may undergo solid-phase interaction, the upper temperature limit is 1000 ºC.