Metall. Res. Technol.
Volume 119, Number 2, 2022
|Number of page(s)||13|
|Published online||27 April 2022|
Austempering of PM HSS ASP2030 for improved fracture toughness
Faculty of Materials Engineering, Sahand University of Technology, P.O. Box 51335/1996 Tabriz, Iran
2 Materials Science and Engineering Department, Delft University of Technology, Delft, Netherlands
3 School of Mechanical Engineering, Vellore Institute of Technology, Vellore, India
* e-mail: Yazdani@sut.ac.ir
Accepted: 2 March 2022
This study presents the fracture toughness improvement of the powder metallurgical high speed steel ASP2030 by replacing the martensitic matrix with a bainitic one. For this purpose, the fracture toughness of the steel is compared in both the austempered and marquenched states. The heat treatment of the samples was carried out by austenitizing in the range of 1150–1185 °C followed by either austempering at 235 °C or marquenching processes. Triple tempering at 560 °C for 2 h was also performed on all specimens. Fracture toughness measurements were performed on circumferentially notched tensile specimens. The microstructural features of the specimens were investigated using X-ray diffraction, optical and electron microscopy, and electron backscatter analysis. The results showed that the fracture toughness is sensitive to small changes in austenitizing temperature at both heat treatment conditions. By increasing the austenitizing temperature from 1150 to 1170 °C, the fracture toughness increases and then decreases with a further increase in temperature to 1185 °C. The results suggest that the changes in fracture toughness are due to the simultaneous effects of the volume fraction of undissolved carbides and the lattice microstrain values at different austenitizing temperatures. It can be concluded that the fracture toughness increases when the martensitic matrix is replaced by a bainitic structure. This improvement is related to finer bainitic laths width and also to the larger spacing between the particles of the undissolved carbides.
Key words: High-speed steel / austempering / marquenching / fracture toughness / microstructural feature
© EDP Sciences, 2022
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.