Interaction of Titanium Diboride with Nickel and Ni–20% Cr Alloy (Nichrome)

The interaction in the Ni–Ti–B and Ni–Ti–B–Cr systems along the Ni–TiB 2 and (Ni–20% Cr)–TiB 2 sections was studied. Solid-phase interaction was not found to occur for Ni–TiB 2 up to 1200°C. In the case of (Ni–20% Cr)–TiB 2 , a new phase was formed, Cr 2 B, with a thickness of ~5 μm at a temperature of 1200°C. The contact melting began above 1200°C in the Ni–TiB 2 system and above 1180°C in the (Ni–20% Cr)–TiB 2 system. In the (Ni–20% Cr)–TiB 2 system, the emerged liquid wetted titanium diboride with an angle of 50°; when temperature increased to 1450°C, the liquid spread completely on the TiB 2 surface. In the contact melting process, several areas formed: titanium diboride area, Ni 3 B and TiB area, Ni and TiB area, and pure nickel. The systems were eutectic and their quasibinary phase diagrams had a eutectic at ~9% TiB 2 with a melting point of ~1200°C at the Ni–TiB 2 section and a melting point of ~1180°C at the (Ni–20% Cr)–TiB 2 section. The alloys in the hypoeutectic part of the phase diagram consisted of the Ni, Ni 3 B, and TiB phases and additionally of the Cr 2 B phase in the (Ni–20% Cr)–TiB 2 system. In the hypereutectic part of the phase diagram, the metal component disappeared and unreacted TiB 2 additionally appeared in the (Ni–20% Cr)–TiB 2 system. Zero solid-phase interaction and contact melting observed at temperatures of 1200 and 1180°C, which were significantly lower than the melting points of the interacting components (Ni, Ni–Cr), promoted favorable conditions for the use of nickel as a metal component in wear-resistant composites produced from granular titanium diboride, capable of operating under dynamic and shock loads at elevated temperatures (~900°C) and in corrosive environments.