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Effects of Laser Quenching on Impact Toughness and Fracture Morphologies of 40CrNiMo High Strength Steel

Effects of Laser Quenching on Impact Toughness and Fracture Morphologies of 40CrNiMo High... The surface of 40CrNiMo steel was quenched with a CO2 laser, Charpy impact test was conducted at temperatures of 20, 0, and −20 °C, and the impact absorption energies were measured. The fracture morphologies were observed with SEM, and the influence of microhardness, residual stress, and retained austenite on mechanical behavior of impact fracture after laser quenching was discussed. The results show that the hardened layer depth is more than 1 mm after laser quenching, and hardness is about 480-500 HV. The fracture morphology of the sample is dimple rupture at a temperature of 20 °C; with the lower temperature the fracture dimples become smaller. At a temperature of −20 °C, the fracture morphologies change from ductile to brittle, which is mainly cleavage fracture. The increase in surface hardness, production of compressive residual stress, and existence of retained austenite after laser quenching are the main mechanisms of increasing impact toughness. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Materials Engineering and Performance Springer Journals

Effects of Laser Quenching on Impact Toughness and Fracture Morphologies of 40CrNiMo High Strength Steel

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References (17)

Publisher
Springer Journals
Copyright
Copyright © 2014 by ASM International
Subject
Material Science; Characterization and Evaluation of Materials; Tribology, Corrosion and Coatings; Quality Control, Reliability, Safety and Risk; Engineering Design
ISSN
1059-9495
eISSN
1544-1024
DOI
10.1007/s11665-014-1164-8
Publisher site
See Article on Publisher Site

Abstract

The surface of 40CrNiMo steel was quenched with a CO2 laser, Charpy impact test was conducted at temperatures of 20, 0, and −20 °C, and the impact absorption energies were measured. The fracture morphologies were observed with SEM, and the influence of microhardness, residual stress, and retained austenite on mechanical behavior of impact fracture after laser quenching was discussed. The results show that the hardened layer depth is more than 1 mm after laser quenching, and hardness is about 480-500 HV. The fracture morphology of the sample is dimple rupture at a temperature of 20 °C; with the lower temperature the fracture dimples become smaller. At a temperature of −20 °C, the fracture morphologies change from ductile to brittle, which is mainly cleavage fracture. The increase in surface hardness, production of compressive residual stress, and existence of retained austenite after laser quenching are the main mechanisms of increasing impact toughness.

Journal

Journal of Materials Engineering and Performance – Springer Journals

Published: Jul 23, 2014

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