ISSUE 3/2011

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Lopez-Galilea, I.; Huth, S. Effect of pressure, temperature and cooling rate on the micro-structural evolution of a single crystal Ni-based superalloy

The single-crystal nickel-based superalloy LEK94, designed for elevated service temperatures in low pressure and intermediate-pressure turbines, has been investigated using Hot Isostatic Pressing (HIP) with respect to microstructural evolution. High pressures of about 100-170 MPa led to local deformations, which close the pores. However, since HIP also requires high temperatures (950-1200 °C) it had a pronounced effect on the microstructure and the local distribution of elements. This contribution analyses the effect of different HIP treatments on both the microstructure and the segregation of the SX superalloy LEK94 in the as-precipitation-hardened state. In addition, the effects of rapid or slow cooling are analyzed for the highest HIP temperature value, 1180 °C. To distinguish the effect of pressure from those of temperature, the HIPed samples are compared with specimens annealed at atmospheric pressure.

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