Microstructural evolution and hot-compressive behavior of Waspaloy forged bolts: experimental and finite element simulation

Abstract

This study aims to present the optimum technological parameters of the hot forging process of aerospace bolts. Deformation-related parameters were determined according to the relevant conditions for commercial production of bolts. Deformation behavior and evolution of the microstructure of Waspaloy were systematically studied at temperature in the range of 1000–1120 °C and strain rate in the range of 0.01–10 s−1. The obtained results revealed the sensitivity of the flow stresses to the deformation parameters and stresses increased when deformed at lower temperatures or higher strain rates. At the high strain rates of 5–10 s−1, the flow curves exhibited a pronounced flow softening. The curves demonstrated a dynamic equilibrium at the low strain rates of 0.01–0.1 s−1. A constituent model of Waspaloy was established to describe the flow characteristic of Waspaloy. The microstructures showed that the grain refinement of DRX at low temperature (1000–1040 °C) was the main mechanism for microstructural evolution, while the grain growth kinetic was the dominant mechanism at high temperature (1080–1120 °C). The DRX kinetic model of this superalloy was established. Also, the constitutive and dynamic recrystallization models were used in the Deform-3D software for validation. The obtained results revealed that the simulation results matched well with the experimental results of grain sizes at different regions of the bolt specimens. The study can provide guidance to optimize technological parameters and predict the microstructure for commercial bolt forging.

Keywords

• Waspaloy
• Flow curves
• DRX kinetics
• Finite element method
• Bolt grain size