Contribution to the study of the Fe-Nb-C ternary system

Abstract

Abstract:In the present paper, solidification sequences are proposed in relation to the observed microstructures for Fe-Nb-C iron based ternary alloys. These alloys are arc melted and characterised by means of differential thermal analysis, scanning electronic microscopy and by quantitative electron probe microanalysis. Thus, an invariant eutectic ternary reaction L ↔ γ + NbC 1-x + Fe 3 C is proposed at 1140°C.

Liquidus Surface Projection of the Fe-Nb-C System in the Iron-Rich Corner

“…The compilation of the results obtained for Nb9 alloy allow us to attribute the peaks appearing on its thermogram (Figure 1 Nb9 and Nb10 alloys present a transformation at about 1140°C. This transformation is attributed to a metastable eutectic ternary reaction, noted E2: L M c(Fe) + NbC 1-x + Fe 3 C. [9] This reaction is in agreement with those occurring in Fe-C and Nb-C binary systems. In fact, the eutectic reaction L M c(Fe) + Fe 3 C in the Fe-C metastable system occurs at 1153°C, [10] and the eutectic reaction L M NbC 1-x + C in the Nb-C system occurs at 3305°C.…”

Microstructure characterisation and mechanical properties of a functionally-graded NbC/high chromium white cast iron composite

“…Therefore, we shall hereinafter refer to this region as the transition region. NbC with a morphology resembling a eutectic phase, commonly referred to in the literature as Chinese-script [13,[27][28][29], can also be observed here. Finally, the rest of the casting (Figures 2fh), constitutes the bulk material, where Chinese-script NbC is predominantly observed and primary NbC particles are rare.…”

“…While this resembles a eutectic reaction, the wide temperature range means that it could be argued that it would be more accurate to refer to it as a "pseudo-eutectic" reaction [16]. However, to be consistent with the established literature, we shall still refer to it as a eutectic reaction [13,[27][28][29]. As the casting cools through this eutectic temperature range (approximately 1290 -1280 o C), the eutectic M7C3 and austenite phase also form.…”

Morphological evolution of NbC particles at the interface of niobium–iron diffusion couple

“…Similarly, the Nb atoms dissolved from the niobium wire diffuse to the interface of the niobium-iron diffusion couple by downward diffusion. Therefore, a Nb-Fe-C ternary system micro-region with a thickness of δ is formed at the interface between cast iron and niobium wire (Figure 7) [20,[24][25][26][27]. In the Nb-Fe-C ternary system micro-region, from niobium wire to cast iron, the concentration of Nb atoms gradually decreases, while the concentration of C atoms gradually increases.…”