Tempering influence on residual stresses and mechanical properties of AISI 4340 steel

• Published in: International journal of advanced manufacturing technology Vol. 120; no. 1-2; pp. 1123 - 1134
• Main Authors: de Souza, Marcel Freitas, Serrão, Luana Ferreira, Pardal, Juan Manuel, Tavares, Sérgio Souto Maior, Fonseca, Maria Cindra
• Format: Journal Article
• Language: English
• Published: London Springer London 01.05.2022; Springer Nature B.V
• Subjects: Barkhausen effect; CAE) and Design; Compressive properties; Computer-Aided Engineering (CAD; Engineering; Hardness; Heat treating; High strength low alloy steels; Industrial and Production Engineering; Mathematical models; Mechanical Engineering; Mechanical properties; Media Management; Model accuracy; Nickel chromium molybdenum steels; Original Article; Residual stress; Tempered martensite; Tempering; X-ray diffraction; Mechanical properties; X-ray diffraction; AISI 4340 steel; Residual stresses; Heat treatments; Magnetic Barkhausen noise
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-022-08880-3

The present work evaluated the tempering temperature influence on microstructure, mechanical properties, and residual stresses of AISI 4340 steel. The residual stresses were measured by X-ray diffraction (XRD) by the sin 2 ψ method and compared to magnetic Barkhausen noise (MBN). The residual stresses exhibited high tensile values after quenching, but a small relief was observed in tempering treatments at 300 °C and 400 °C, which also presented a hardness decrease compared to the as-quenched condition. XRD and MBN analyses indicated that residual stresses became compressive in tempering performed between 500 and 650 °C. Therefore, compressive residual stresses combined with appropriate hardness and toughness values (35 HRC and 33 J) obtained from 500 °C tempering temperature can be used to improve the mechanical properties of AISI 4340 steel components. Additionally, a mathematical model was established to estimate the tempered martensite hardness for different tempering temperature conditions. This model showed high accuracy ( R 2  = 0.99) for a holding time of 90 min.