Basic Structure of A Ni-base Superalloy GH220

The structures of standard heat treatment of the alloy have the phases of gamma, gamma prime, MC,M₆C and M₃B₂.
The first temperature rang of grain growth is about 1150-1170℃. The second is 1210℃. The maximum precipitation peak of main carbide phase M₆C is about 1000℃, and two kinds of M₆C differentiated between in compositions has been found in the tested alloys.
The standard heat trearment of the alloy do not get two kinds of gamma prime phase in size, but the isothermal treatment can get two kinds of gamma prime phase and zigzag grain boundary. The phase of M₂₃C₆ after ageing for a long time can be precipitated in the alloy which has low content of Mo, W, Al and Ti, If the content of W,Mo is greater than 12% （e.g 12.31%）, a few Mu phases can be precipitated.
The carbide can be changed in shape and fined in size,when the magnesinm is added to alloy.