BS in Materials Engineering
Materials Engineering Department
Samples of Haynes 230 nickel-based superalloy were taken from forgings at Carlton Forge Works. These samples represented components that passed and failed ductility specification. Metallographic measurements of particle size and intergranular particle count were taken from 25 locations across the sample. Carbide particles at the grain boundaries were equal size, averaging 13.0 μm in diameter. The low ductility samples contained an average of twelve particles per 250 μm of grain boundary, high ductility samples contained an average of only four particles along the same grain boundary length. To determine the effects of forging temperature on carbide distribution in the microstructure, three 4-in-diameter, 4-in-height Haynes 230 billets were upset forged to 7-in-diameter, 1-in-height at 2050°F, 2150°F, and 2250°F. For each forging, samples were removed and solutionized at 2150°F, 2200°F, and 2250°F for 45 minutes. Each combination of forging temperature and solutionizing temperature was tensile tested to determine yield strength and ductility. Results showed the alloy increased ductility with forging temperature, which corresponded to decreased particle count. Mechanical properties were altered less prominently with solutionizing temperature, but a small increase in tensile strength and decrease in ductility was associated with higher temperature solutionizing, accompanied by a decreased particle size. Particle count and distribution were found to the key factor in determining ductility of the material. Forging at low temperatures causes plastic deformation at the grain boundaries, providing a low energy nucleation site for migrating carbon in solution, thereby increasing the number of particles in the forged pieces. The optimal combination of ductility and yield strength occurred at 2150°F forging temperature and 2200°F solutionizing temperature.