Steels with High Temperature Carbides - New Possibilities for Semi-Solid State Processing

Abstract:

Semi-solid processing of steels is typically studied using high-alloy steels with higher carbon levels, as those offer a long freezing range which is favourable for conducting the process. The drawback to their application is their microstructure which typically consists of austenite grains embedded in ledeburitic network. This type of microstructure typically fails in brittle manner by fracturing along the interface of the hard network and ductile austenite grains. This is why a way was sought to altering or even inverting the configuration of the microstructure. Eventually, suitable steel chemistries were found which allow the inverted microstructure to be obtained. With regard to the high content of alloy additions, these steels have to be made by powder metallurgy methods. Five different steels of this kind were selected for the experimental programme. All contained high amounts of alloying elements and a large fraction of carbides. Their carbon content was taken into account as well, ranging from 0.55 to 3.4 %. Differences between the steels consisted in the levels of major alloying elements, namely chromium, vanadium, molybdenum, tungsten and cobalt. After suitable process parameters were found, semi-solid processing was used to prepare demonstration products. The transition through semi-solid state transformed the ferritic matrix to austenitic-martensitic one, in which the high-stability carbides were retained. The resulting microstructures were of unconventional nature where carbide particles were embedded in tough metal matrix. Their configuration was thus inverted in contrast to the ones typically obtained by semi-solid processing of tool steels.

• Periodical: Solid State Phenomena (Volumes 217-218)
• Pages: 325-331
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.217-218.325
• Online since: September 2014
• Authors: Hana Jirková*, Kateřina Rubešová, Vít Pileček, Mária Behúlová
• Keywords: Mini-Thixoforming, Powder metallurgy, Semi-Solid Processing, Unconventional Structures of Tool Steels

References

[1] P. Cezard, T. Sourmail, Thixoforming of Steel: A State of the Art from an Industrial Point of View, Solid State Phnenomena 141-143 (2008) 25-33.

DOI: 10.4028/www.scientific.net/ssp.141-143.25

[2] B. Amin-Ahmadi, H. Aashuri, Semi-solid Structure for M2 High Speed Steel Prepared by Cooling Slope, Journal of Materials Processing Technology 210 (2010) 1632-1635.

DOI: 10.1016/j.jmatprotec.2010.05.011

[3] H. V. Atkinson, Alloys for Semi-Solid Processing, Solid State Phenomena 192-193 (2013) 16-27.

DOI: 10.4028/www.scientific.net/ssp.192-193.16

[4] B. Masek, et al., Structure of Miniature Components from Steel Produced by Forming in Semi-solid State, Transactions of Nonferrous Metals Society of China 20 (2010) 1037-1041.

DOI: 10.1016/s1003-6326(10)60627-9

[5] D. I. Uhlenhout, J. Kradolfer, W. Püttgen, J. F. Löffler, P. J. Uggowitzer, Structure and properties of a hypoeutectic chromium steel processed in the semi-solid state, Acta Materialia 54 (2006) 2727-2734.

DOI: 10.1016/j.actamat.2006.02.021

[6] W. Püttgen, B. Hallstedt, W. Bleck, P. J. Uggowitzer, On the microstructure formation in chromium steels rapidly cooled from the semi-solid state, Acta Materialia 55 (2007) 1033–1042.

DOI: 10.1016/j.actamat.2006.09.021

[7] M. Z. Omar, E.J. Palmiere, A.A. Howe, H.V. Atkinson, P. Kapranos, Thixoforming of a high performance HP9/4/30 steel, Materials Science and Engineering A 395 (2005) 53–61.

DOI: 10.1016/j.msea.2004.12.013

[8] I. Sen, H. Jirkova, B. Masek, M. Böhme, M.F. -X. Wagner, Microstructure and mechanical behavior of a mini-thixoformed tool steel, Metall. Mater. Trans. A, 43 (2012), 3034–3038.

DOI: 10.1007/s11661-012-1305-3

[9] H. Jirkova, et al., Mini-thixoforming of a steel produced by powder metallurgy, Solid State Phenom. 192–193 (2013), 500–505.

DOI: 10.4028/www.scientific.net/ssp.192-193.500

[10] D. Aišman, H. Jirková, M. Behulová, B. Mašek, Influence of Cavity Shape and Entry Hole on Minithixoforming, METAL 2011, Ostrava : TANGER, 2011, 210-215, ISBN: 978-80-87294-24-6.

[11] Mašek, B.; Aišman, D.; Jirková, H.; Wurster, S., Micro-Compression Test of Thixoformed Austenite in: Solid State Phenomena 192-193 (2013), 215-218.

DOI: 10.4028/www.scientific.net/ssp.192-193.215

[12] JMatPro – Practical Software for materials Properties, Version 6. 1, <http: /www. sentesoftware. co. uk>, (accessed 05/2013).

[13] D. Aišman, K. Rubešová, Š. Mikmeková, Mini-thixoforming of High-Alloyed CPM REX 121 Steel, Advanced Materials Research 887-888 (2014) 1156-1160.

DOI: 10.4028/www.scientific.net/amr.887-888.1156