Effects of Different Austenitizing Times on the Microstructure and Properties of Cr-Ni-Mo-V Series High-Strength Steels

Abstract

Herein, the effects of varying austenitizing times on the microstructure and mechanical properties of Cr-Ni-Mo-V series high-strength steel are investigated, discussing the mechanisms that enhance strength and toughness. By controlling the austenitizing duration, the microstructure during subsequent heat treatments is improved, leading to enhanced overall mechanical properties. The experimental steel undergoes treatments at different austenitizing times, and the microstructure is characterized using optical microscopy, energy-dispersive spectroscopy, field emission scanning electron microscopy, and X-ray diffraction. Mechanical properties are assessed through tensile testing, impact testing, and microhardness measurements. The results indicate that, when comparing an austenitizing time of 1 to 1 h and 15 min, the ultimate tensile strength decreases by 10%, microhardness reduces by 78.2 HV, elongation increases by 1.39 times, and toughness improves by 80%. The enhancement in toughness is primarily attributed to the synergistic effect of tempered martensite and bainite within the microstructure. Fracture morphology analysis reveals that variations in austenitizing time affect carbide distribution, accelerate carbide dissolution, decrease the crack growth zone, and enhance toughness. This study provides valuable insights for designing Cr-Ni-Mo-V series high-strength steels with optimal strength-toughness synergies.