# Coordinated Regulation of Mechanical Behavior and Residual Stress of 9Cr-3W-3Co Steel Based on Jominy Test

## TL;DR

This paper studies how to optimize the mechanical properties and residual stress in a heat-resistant steel used in power units through heat treatment and quenching.

## Contribution

The study combines numerical simulation and Jominy tests to optimize heat treatment parameters for 9Cr-3W-3Co steel.

## Key findings

- Martensite, grain refinement, and carbide distribution significantly influence quenching hardness.
- Austenitizing at 950°C achieves over 35 HRC hardness within 50 mm depth after quenching.
- Optimized parameters reduced maximum residual stress by 11.8% compared to 1000°C austenitizing.

## Abstract

Heat-resistant steel 9Cr-3W-3Co is one of the most important materials of advanced ultra-supercritical units. Investigating the quenching performance of 9Cr-3W-3Co material and optimizing its post-quenching microstructural mechanical properties and residual stress distribution are crucial for ensuring the service performance of large forgings. In this paper, the relevant research was carried out based on the combination of numerical simulation and the Jominy end-quenching test. The microstructure evolution and mechanical properties formation mechanism under different austenitizing temperatures were studied first. Furthermore, considering the residual stress distribution, the heat treatment parameters were optimized. The results showed that the martensite, grain refinement, and carbide distribution of the material were the key factors affecting the hardness after the quenching process. When the austenitizing temperature was 950 °C, a hardness of more than 35 HRC can be obtained within a 50 mm depth after quenching. Meanwhile, on the basis of balancing thermal stress and phase transformation stress, the maximum residual stress decreased by 11.8% compared with that obtained at a 1000 °C austenitizing temperature, dropping to 608 MPa.