Effect of the Particle Size of γ’ Phase on the Mechanical Properties of Ni Base Superalloy

Abstract

The effect of γ’ particle size upon the mechanical properties of Ni base superalloy EP741NP obtained by powder metallurgy was investigated. The particle size of γ’ phase in γ-γ’ microstructure was varied by changing the cooling rate V from the temperature of the solid solution treatment at 1200 °C (V = 80, 200 and 400 °C \ min.). After solid solution treatment billets were subjected to aging in the standard mode. It was established that as V increases from 80 to 200 °C \ min., the average particle’s size of γ’ phase decreases from 0.54 microns to 0.22 microns in the aged state. This improves the characteristics of creep and low cycle fatigue at 650°C: time to rupture under load 1000 MPa increased from 132 hours to 416 hours and low cycle fatigue increased from 42,215 to 82,016 cycles.