Furnace cart assembly for loading high temperature vacuum furnaces for treating target material, for example, metal parts, under extreme temperature and vacuum environments. The furnace cart includes electrical heating elements as an integral part of the cart, which elements are adapted for releasable connection to the furnace electrical supply. When so connected the furnace cart heating elements can form a part of the heating system of the furnace. The lower part of the furnace cart assembly, including a frame above and supported on wheels, the frame having heat reflection means on at least Its upper surfaces providing some protection from heat is preferably also protected from heat during furnace operation by insulating material above the frame (the material desirably supported by the frame but separated therefrom).