Structural transformations of gas-thermal coating of Ni60Nb40 alloy under vacuum annealing

Structural transformations in gas-thermal Ni60Nb40 alloy coatings are studied during isothermal annealing within the 300-1360 K temperature range. Electron microscopy, X-ray technique and differential thermal analyses reveal mainly the amorphous structure of initial coatings in the presence of crystalline inclusions of NbO2, Ni3Nb, Ni and NiO. The amorphous structure decay which begins at 800 K by isolation of Ni3Nb is accompanied by a loss of the coating elesticity and plasticity and by changes in fracture surfaces morphology. The inverse sequence of stable phases precipitation is observed as compared with the crystallization of amorphous band alloys of the same composition