Preparation method of ultrafine grain nickel base powder high temperature alloy

A preparation method of an ultrafine grain nickel base powder high temperature alloy belongs to the technical field of high temperature alloy. Pinning effect of crystal boundary gamma' particle during thermal deformation is utilized; powder high temperature alloy ingot is heated in air to a temperature 40-80 DEG C lower than a complete dissolving temperature of a gamma' hardening constituent thereof, treated with multiple heating quasi isothermal forging to reach a ingot accumulation deflection of higher than 75% and treated with recrystallization annealing to obtain a cake blank with uniform structure and grain size of grade 10-12. The invention has the following advantages: quasi isothermal forging with gross distortion of powder high temperature alloy can be realized to obtain ultrafine grain cake blank; production organization is simple and highly operational, so as to effectively solve a problem of processing powder high temperature alloy into uniform ultrafine grain by hot working; and produced cake blank has large deflection, so as to facilitate elimination of residual dendrite and original particle boundary in an isostatic pressing state tissue; product quality is good; production efficiency is high; and cost is low.