CONTACT INTERACTION OF ZIRCONIUM DIBORIDE WITH NICKEL AND NICKEL ALLOYS.
II. CONTACT INTERACTION IN THE ZIRCONIUM BORIDE–NICHROME SYSTEM

Abstract

Zirconium boride–nichrome (Ni–20 Cr) interaction at zirconium boride concentration varying from 3.6 to 60% in the charge and annealing temperatures of 1100–1850 °С has been studied. It is shown that the process begins at 1200 °С as a solid-phase reaction to form nickel borides. At 1300–1350 °С, contact fusion that is characteristic of eutectic systems follows the solid-phase interaction. A liquid of eutectic composition appears and wets zirconium boride with a contact angle of 0° at 1500 °C. The eutectic melting point is 1320 ± 20 °C at a zirconium boride concentration of 11–13% in the alloy. The phase composition of the interaction products depends on the ratio of alloy components and temperature. It is represented by double and triple compounds in the Ni–Cr–B–(in part) C system formed from chromium and nickel boride crystal lattices. The main part of zirconium in the alloy is concentrated in the formed intermetallides. Thus, the contact pairs made of zirconium–nichrome boride materials can operate only at temperatures below 1200 °C.