Preparation of Globular Microstructure in H18 Steel for Semi Solid Processing with the Use of Boron Addition

Abstract:

Martensitic stainless steel was chosen for a semi-solid processing due to high mechanical properties and resistance to high temperature surface oxidation. Modified H18 martensitic steel (1.1 % - C, 18.9 % - Cr, 0.1 % - V, 0.7 % - Mo, 0,9 % - Si, 2.0 % - Mn, balance Fe, all in weight %) modified with addition of 0.01 % boron was applied as a feedstock for semi-solid range temperature experiments. The samples were heated up to 1330°C to obtain about 26% of the liquid phase followed by rapid quenching in water. The microstructure of the samples consisted of austenitic globular grains (average grain size 42 μm, about 78 % of volume) surrounded by a eutectic mixture (ferrite, and M₇C_3, M₂₃C₆ carbides as identified by X-ray and electron diffraction). The initial hardness of as-cast sample was 357 HV₅ and that after quenching from liquidus solidus range was 422 HV₅. The X-ray analysis confirmed the presence of 16% - α-Fe, 80% - γ-Fe and 4% - M₇C₃ carbides in rapid quenched sample. The EDS analysis of a eutectic mixture was as follows: 6.2 % - C, 31.7 % Cr, 0.1 % - Mn, 0.6 % - Si, 61.2 % Fe. The chemical composition analysis of globular grains confirmed the presence of 2.0% C, 16.3 % - Cr, 1 % - Si, 1.7 % - Mn, 0.5 % - Mo, 78.5% Fe.

• Periodical: Solid State Phenomena (Volumes 217-218)
• Pages: 8-14
• DOI: https://doi.org/10.4028/www.scientific.net/SSP.217-218.8
• Online since: September 2014
• Authors: Jan Dutkiewicz, Jan Głownia, Łukasz Rogal*
• Keywords: Modification, Semi-Solid Metal Processing (SSM), Stainless Chromium Martensitic Steel

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