Öncü AKYILDIZ, Bülent ALKAN, Selin TORAMAN, Tugay COSGUN, Baris CETİN

KÜRESEL GRAFİTLİ DÖKME DEMİRLERDE FAZLARIN HACİM ORANI, NODÜLARİTE VE NODÜL SAYISININ IMAGEJ YAZILIM PROGRAMI KULLANILARAK DEĞERLENDİRİLMESİ

Bu çalışmada, küresel grafitli dökme demirlerin mikro yapılarını nicel olarak tanımlamak için ücretsiz dijital görüntü işleme yazılımının kullanıldığı basit bir yöntem açıklanmıştır. Yöntem üç farklı küresel grafitli dökme demir türüne uygulanarak, bunların içyapılarındaki ferrit, perlit ve grafit faz oranları, grafit nodülerliği, nodül sayısı, nodül büyüklüğünü değerlendirilmiştir. Örneklerin iyi derecede nodülerlik (alana göre ~ % 88) gösterdiği, farklı grafit ortalama büyüklüğüne ve çevre morfolojisine sahip oldukları bulunmuştur. Tüm örneklerde grafit miktarının da benzer olduğu (alana göre % 11 ± 2) bulunmuştur. Öte yandan, ASTM A536 sınıfları 60-40-18, 65-45-12 ve 80-55-06 için ferrit yüzdeleri sırasıyla % 85.8, 57.1 ve% 52.5 olarak hesaplanmıştır. Ayrıca, bu üç sınıf arasında, perlit içeriği arttıkça sertliğin arttığı gösterilmiştir. Sonuçların standartlar ile uyumlu olması, görüntü işleme yoluyla kantitatif metalografinin dökme demirlerin mekanik özelliklerini tahmin etmek için güçlü bir araç olduğunu göstermiştir.

ASSESSING THE VOLUME FRACTIONS OF THE PHASES, NODULARITY AND NODULE COUNT OF SPHEROIDAL GRAPHITE CAST IRON USING IMAGEJ SOFTWARE

In this study, a simple method for assessing the microstructure of ductile cast iron by using a freeware digital imageprocessing software is described. The method is applied to three different ductile iron grades to assess their ferrite, pearliteand graphite volume fractions as well as graphite nodularity, nodule count, nodule size. All specimens were found to showgood nodularity (~ 88 % by area) with different graphite average size and perimeter morphology. The amount of graphitewas also found to be similar (11±2 % by area) in all specimens. On the other hand, ferrite percentages were found as 85.8,57.1, and 52.5 % respectively for ASTM A536 grades 60-40-18, 65-45-12, and 80-55-06. It was also found that among thesethree grades, the higher the pearlite content, the higher the hardness. The agreement with the standards confirms thatquantitative metallography through image processing is a powerful tool in order to estimate the mechanical properties ofcast irons.

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