Scanning electron microscopy studies with energy dispersive x-ray analyses of as-cast and annealed samples of Ni-Ru-Y were used to produce a solidification projection, a liquidus projection surface and an isothermal section at 1200 °C. The ~YNi 2 , ~YNi 3 and ~YRu 2 phases had wider solubilities than line compounds, and also extended the furthest into the system. The binary phase extensions into the ternary were: ~51 at.% Ru for ~YNi 2 ; ~22 at.% Ru for ~YNi 3 ; ~13 at.% Ru for ~YNi 5 ; ~7 at.% Ru for ~YNi; ~12 at.% Ni for ~YRu 2 and ~10 at.% for ~Y 44 Ru 25 . Ruthenium stabilised ~YNi 2 , so that it solidified at a higher temperature in the ternary than in the Ni-Y binary. A ternary phase was confirmed at Y 51 Ru 15 Ni 34 (at.%), which forms in a peritectic reaction. The ~Y 3 Ru and ~Y 3 Ni phases were isomorphous and formed a continuous solid solution. Heat treatment at 1200 °C gave the phases: (Ru), ~YRu 2 , ~YNi 2 , ~YNi 3 , ~YNi 4 , ~YNi 5 and (Y).