EFEITO DA ADIÇÃO DE Nb NA MICROESTRUTURA DE FERRO FUNDIDO BRANCO ALTO CROMO HIPEREUTÉTICO

Pacheco, Dimas de Andrade; Godoy, Geralda Cristina; Oliveira, Cláudio Gonçalves de; Antônio, Loudiana Mosqueira; Bueno, Mário José

doi:10.5151/1516-392x-30492

Cited by 1 publication

(2 citation statements)

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“…In Figure 8, it is possible to notice a statistically significant reduction of CVF, which corroborates with the results and microstructural alterations observed by Fiset et al [7], Filipovic [8] and Pacheco [12]. The morphology change, from a quasi-eutectic microstructure to a hypoeutectic one, and the CVF reduction occur because niobium is a strong carbide forming and has higher melting temperature (3500ºC) than the high Cr liquid [21].…”

Section: Resultssupporting

confidence: 86%

“…Controlled additions of niobium in HCCI alloys reduce the volume fraction of primary and/or eutectic carbides, which makes it possible for an alloy with "initial" chemical composition of hypereutectic to result in a eutectic alloy [6][7][8]12]. These alloys exhibit NbC and showed higher resistance to abrasion when compared to alloys that did not experienced niobium addition 13.…”

Section: Introductionmentioning

confidence: 99%

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Effect of niobium addition on the properties and microstructure of a high chromium cast iron alloy

Melo

Silva

et al. 2020

Matéria (Rio J.)

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High chromium cast iron (HCCI) is usually employed in equipment that experience high abrasive wear and therefore requires high resistance. Niobium could be added to these alloys to improve their resistance to wear. This study consisted in addressing the influence of 0.5% and 1.0% of niobium on the microstructure of a 26% Cr and 2.8% C HCCI alloy. Standard sampleswithout niobiumand samples with 0.5% and 1.0% Nb were melted, cut and then machined into adequate dimensions for tests. Two groups of sampleswith and without heat treatmentwere analyzed through X-ray Diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), Vickers and Rockwell-C hardness. Carbides Volume Fraction (CVF) was quantified in the heat-treated samples. The majority of NbC carbides were observed to be thin and presented a hook shaped morphology. In addition, it was noted a precipitation of Nb-rich layers around the M 7 C 3 carbides, which could act as a higher hardness coating. There was significant reduction in carbide volume fraction, from an initial 33.3% to 28.1% for the 0.5 % Nb alloy, and further reduction to 24.9% for the 1.0% Nb alloy, it was also noted an alteration on the quasi-eutectic microstructure to a hypoeutectic microstructure. The NbC carbides prevented hardness reduction as a result of lowering the CVF in heat-treated alloys; however, the alloys without heat treatment experienced reductions in hardness.

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Section: Resultssupporting

confidence: 86%