Characterization of precipitates in a 2.25Cr–1Mo–0.25V steel for large-scale cast-forged products

• Published in: Materials characterization Vol. 58; no. 10; pp. 968 - 973
• Main Authors: Fu, R.D., Wang, T.S., Zhou, W.H., Zhang, W.H., Zhang, F.C.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.10.2007; Elsevier Science
• Subjects: CARBIDES; CHROMIUM ALLOYS; Cross-disciplinary physics: materials science; rheology; Cr–Mo–V steel; Exact sciences and technology; GRAIN BOUNDARIES; MATERIALS SCIENCE; MOLYBDENUM ALLOYS; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; PRECIPITATION; QUENCHING; Solidification; STEELS; TEM; TEMPERATURE RANGE 0400-1000 K; TEMPERATURE RANGE 1000-4000 K; TEMPERING; TRANSMISSION ELECTRON MICROSCOPY; VANADIUM ADDITIONS; Precipitation; Tempering; TEM; Cr–Mo–V steel; Quenching; Transmission electron microscopy; Cr-Mo-V steel; Microstructure; Precipitates; Heat treatments
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2006.10.002

In this paper, the precipitates formed during the heat-treatment processes for 2.25Cr–1Mo–0.25V steels were investigated by using an analytical transmission electron microscope (A-TEM). The results show that the complex precipitates containing several microalloyed elements (Ti, Nb, V) are dominant when the specimens are re-austenitized at 980 °C and 1200 °C. When the austenitization temperature is increased, the size and the quantity of the precipitates decrease. It is worth noting that Nb and V still exist in the precipitates even when the austenitizing temperature is as high as 1200 °C. It indicates that the composition of the complex precipitates has become homogeneous during prior thermal processing. Some vanadium is also preserved in the core of the complex precipitates. For the specimen quenched from 980 °C and tempered at 650 °C for 30 h, numerous carbides (e.g.; M 23C 6, M 2C and M 7C 3) are formed along grain boundary or in the matrix, in which elements such as Fe, Mn, Cr, Mo and V are found. Moreover, the prior precipitates have become coarse due to the extended tempering time.