The Effects of Homogenizing and Quenching and Tempering Treatments on Crack Healing

Yao Qiu,Jianbin Luo,Qingxian Ma,Ruishan Xin

doi:10.3390/met10040427

Abstract

After thermal deformation and heat treatment, it can be observed that there are small, newly formed grains in the crack healing zone, which indicates that the internal crack is fully healed. However, in our previous study, the impact properties of the internal healing zone could only be partially healed. In this study, the process of homogenizing treatment was adopted to achieve grain size homogeneity. The effects of homogenizing treatment and quenching and tempering treatment on crack healing were also systematically analyzed. With the same heat treatment method, SA508-3 samples, which were subjected to multi-pass deformation, had a higher percentage recovery than those that underwent uniaxial compression. The percentage recovery of the crack healing zone was significantly improved after the process of homogenizing treatment. The impact property of the crack healing zone could be fully restored after homogenizing treatment followed by quenching and tempering treatment. However, after several episodes of heating, the grain-boundary strength decreased, and the impact value was relatively low.

Highlights

In the manufacturing process, it can be observed that internal defects appear inside large forgings such as porosities and internal cracks
Several methods were used for crack healing, including the isothermal heat treatment method [1,2,3], thermal deformation [4,5,6,7], and the electropulsing technique [8,9]
The homogeneity in carbide distribution between the crack healing zone and the matrix could be affected by the homogeneity of grain sizes

Summary

Introduction

It can be observed that internal defects appear inside large forgings such as porosities and internal cracks. In the production of large forgings, the thermal deformation method followed by annealing is often used in internal crack healing. Han et al [1,2] and Xin et al [3] showed that after isothermal heat treatment at 1100 ◦ C or a higher temperature, crack healing in steel could be achieved. Meng et al [5] discovered that fine grains were formed in the process of crack healing. These grains firstly formed on the surface of the internal crack, and their morphology was different from that of the matrix. Xin et al [6] and Qiu et al [7] found that after annealing from the healing temperature, the tensile property could be fully restored, but the impact properties could only be partially restored, and this was related to the inhomogeneity of grain sizes

Objectives

Methods

Findings

Conclusion