Identification of carbonitride precipitates in a 1wt.%Cr0.5wt.%Mo steel using analytical electron microscopy

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The initial stages of carbonitride precipitation, in a normalized 1wt.%Cr0.5wt.%Mo steel subjected to isothermal heat treatment at 600 and 650°C, have been studied using electron microdiffraction, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. In the asnormalized steel, fine-scale (100 nm) equiaxed particles of f.c.c. CrN (a = 0.414 nm) have been identified at ferrite grain boundaries. With isothermal aging, an apparently continuous change in composition is observed in these grain boundary particles, forming firstly cubic close-packed carbonitrides (Cr, Mo) (N, C), followed by a transition to h.c.p. (Mo, Cr)2 (C, N) and eventual formation of Mo2C. Within the ferrite grains, short elliptical precipitate rods are detectable in extraction replicas from specimens aged for 25 h at 650 °C. These particles have been identified as h.c.p. Mo2C. No significant changes in composition or structure were observed to accompany the growth of these intraferritic particles during isothermal aging.

Original languageEnglish
Pages (from-to)123-132
Number of pages10
JournalMaterials Science and Engineering A: Structural Materials: Properties, Microstructure and Processing
Issue number1
Publication statusPublished - 10 Jan 1991

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