Carbide Dissolution Kinetics during Partial and Full Austenitization in 100Cr6 Steel

Yıl 2020, , 597 - 604, 01.09.2020

Ersoy Erişir , Ahmet Efe Gezmişoğlu

https://doi.org/10.2339/politeknik.556964

Öz

In this work, cementite dissolution kinetics was
studied in 100Cr6 steel during partial and full austenitization. The change in
cementite volume fraction and size was determined from samples heat treated for
different durations at 840 °C and 1050 °C. The SEM micrographs were analyzed by
using ImageJ software to count size and volume fraction of carbides. The
obtained statistical data were used to draw the dissolution curves with a
nonlinear curve fitting method. It was found that the cementite dissolution
rate is fast at the beginning of partial and full austenitization. A model was
established and carbide dissolution was calculated using DICTRA software. The
dissolution curves were obtained and compared with the DICTRA simulations. The
calculation results are in good agreement with the dissolution curves from
statistical results of SEM micrographs. According to the calculation results,
the fast carbide dissolution is due to dissolution under non-partitioning local
equilibrium (NPLE) mode controlled by diffusion of C atoms and neglecting
diffusion of Cr. 

Anahtar Kelimeler

Austenitization, kinetic simulations, dissolution kinetics, image analysis, imageJ

100Cr6 Çeliğinde Kısmi ve Tam Östenitlemede Karbür Çözünmesi Kinetiği

Öz

Bu
çalışmada, 100Cr6 çeliğinde kısmi ve tam östenitleme koşullarında sementit
çözünme kinetiği incelenmiştir. 840 °C ve 1050 °C sıcaklıkta farklı sürelerde
ısıl işleme tabi tutulan numunelerde sementit hacim oranındaki ve boyutundaki
değişim belirlenmiştir. ImageJ yazılımı ile SEM mikrografları analiz edilerek
karbürlerin boyutu ve hacim oranları belirlenmiştir. Elde edilen istatistiksel
veriler “lineer olmayan eğri uydurma” yöntemi kullanılarak çözünme eğrilerine
dönüştürülmüştür. Tam ve kısmi östenitleme işlemlerinin başlangıcında sementit
çözünme hazının yüksek olduğu belirlenmiştir. Bir model kurularak DICTRA
yazılımında karbür çözünmesi hesaplanmıştır. Elde edilen çözünme eğrileri
DICTRA sonuçları ile karşılaştırılmıştır. SEM mikrograflarından elde edilen
istatistikler ile DICTRA hesaplamalarının uyumlu olduğu görülmüştür. Elde
edilen hesaplama sonuçlarına göre başlangıçtaki hızlı karbür çözünmesinin
nedeni, C atomları difüzyonu ile kontrol edilen ve Cr difüzyonunun ihmal
edildiği “ihmal edilebilir yerel denge” modunda çözünmenin gerçekleşmesidir.

Anahtar Kelimeler

Östenitleme, kinetik simülasyon, çözünme kinetiği, görüntü analizi, ımageJ

Kaynakça

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