Effect of Carbon Content on the Microstructure and Mechanical Properties of Hyness 25 Superalloy

The effects of 0.05, 0.1 and 0.15 wt% C on the microstructure, hardness and tensile properties of annealed Haynes 25 were investigated. The alloys were melted in a vacuum induction melting furnace and purified through electro slag remelting process then solution annealed at 1200˚C for 30 min. The results indicated that W-riched M6C carbides developed in the microstructure and its amount increase with increase of carbon. By increase of Carbon from 0.05 to 0.15wt%, grain size decrease from 44 to 35 µm. The carbides act as nucleator and also retard grain growth that cause to reduce grain size. Mechanical properties investigation shows that with increasing carbon, as a result of grain refinement and the proper size and morphology of carbides, hardness increases from 255 to 290 Hv, yield strength from 450 to 510 MPa and ultimate tensile strength from 946 to 1088 MPa but ductility decreases slightly.