High-temperature metallurgy of advanced borated stainless steels

Autor: Charles V. Robino, M. J. Cieslak
Rok vydání: 1995
Předmět:
Zdroj: Metallurgical and Materials Transactions A. 26:1673-1685
ISSN: 1543-1940
1073-5623
DOI: 10.1007/bf02670754
Popis: The high-temperature metallurgy of advanced borated stainless steels has been evaluated through differential thermal analysis, aging studies, quantitative metallography, and impact toughness measurements. Differential thermal analysis (DTA) was conducted on alloys containing a range of boron concentrations and was used to determine the temperatures associated with melting/ solidification reactions. Aging studies, conducted at temperatures near the solidus, were used to determine the effects of elevated temperature exposures on impact properties and micro-structure. Differential thermal analysis quantified the solidus and liquidus temperatures as a function of boron concentration. Impact testing of samples aged at temperatures near the solidus indicated only moderate reductions in toughness. Particle shape measurements indicated that the boride particles were initially nearly spherical and remained so during elevated temperature exposure, although some faceting and agglomeration of the borides did occur. Measurements of boride particle size distributions were used to define the time, temperature, and composition dependence of the boride coarsening. Coarsening data were analyzed in terms of current coars-ening models. These analyses indicated that the boride particle coarsening followed the theo-retically predictedt1/3 time dependence and that the coarsening rate increased with increasing volume fraction of the boride phase. Analysis of the particle size data for aging at various temperatures indicated that the boride coarsening was consistent with the activation energy for Cr diffusion in austenite. Scanning electron microscopy of the impact fracture surfaces showed that the failure mode in isothermally heat-treated samples was ductile and essentially identical to the failure mode for as-received material.
Databáze: OpenAIRE
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