Evaluation of Workability on the Microstructure and Mechanical Property of Modified 9Cr-2W Steel for Fuel Cladding by Cold Drawing Process and Intermediate Heat Treatment Condition

Abstract

In this study, we evaluated the cold drawing workability of two kinds of modified 9Cr-2W steel containing different contents of boron and nitrogen depending on the temperature and time of normalizing and tempering treatments. Using ring compression tests at room temperature, the effect of intermediate heat treatment condition on workability was investigated. It was found that the prior austenite grain size can be changed by the austenite transformation and that the grain size increases with increasing temperature during normalizing heat treatment. Alloy B and Alloy N showed different patterns after normalizing heat treatment. Alloy N had higher stress than Alloy B, and the reduction in alloy N increased while the reduction in alloy B decreased. Alloy B showed a larger number of initially formed cracks and a larger average crack length than Alloy N. Crack length and number increased proportionally in Alloy B as the stress increased. Alloy B had lower crack resistance than Alloy N due to boron segregation.

Effects of Tempering Temperature on the Microstructure and Mechanical Properties of T92 Heat-Resistant Steel

“…With increasing tempering temperature, no significant change in the grain size of the primary austenite was observed, while the martensite laths became clearer and more uniform. It was reported that the grain size of the prior austenite was related to normalizing heat treatment [11], increasing with the increasing temperature during the normalizing heat treatment, while the normalizing temperature was unchanged in this work. The mean size of the prior austenite grains and the length of the martensite laths are shown in the Table 2, and none of them had an obvious correlation with the tempering temperature.…”

“…The microstructure evolution results in the deterioration of the mechanical properties of T92 steel. Heat treatment had important effects on both the microstructure [5,10,11] and mechanical properties [5,11] of 9Cr F/M steels, and it has been reported that the key to improve the high temperature properties of T92 steel is to precipitate enough dispersed carbonitrides in the pre-treatment stage [12], which can remain stable during long-term high temperature service. The common heat treatment of T92 steel includes a normalizing process, following tempering process [13].…”

Influence of Heat Treatment on the Workability of Modified 9Cr-2W Steel with Higher B Content

“…The applicability of the compression test as a general method for evaluating the cold workability of steel has been investigated [16][17][18]. Compression tests were carried out at 298 K and the strain rate of 1 mm/min using an INSTRON-3367 (INSTRON, Norwood, MA, USA) system to evaluate the mechanical properties and workability of the alloy B and Gr.92 specimens subjected to the different heat treatment processes.…”