Farklı Martenzit Hacim Oranlarında Kırılma Tokluğu Değerlerinin İncelenmesi

Abstract

Bu çalışmada AISI 4140 ve AISI 4340 çeliklerde martenzit hacim oranlarının sertlik ve kırılma tokluğu üzerindeki etkisi incelenmiştir. Çeliklerin ara kritik sıcaklık aralıkları belirlenerek üçer farklı sıcaklıkta su verme işlemi, ardından görüntü işleme yöntemi ile içyapı görüntüleri üzerinde her koşul için martenzit hacim oranı belirlenmiştir. Ara kritik sıcaklığın artmasıyla martenzit hacim oranları artış göstermiştir. Numunelere sertlik ve kırılma tokluğu testleri uygulanmış, martenzit miktarının artmasıyla numunelerin sertlikleri artarken kırılma tokluğunun azaldığı belirlenmiştir. AISI 4340’ın, AISI 4140’a göre daha yüksek sertlik değerlerine sahip olmasına rağmen daha düşük kırılma tokluk değerlerine sahip olduğu görülmüştür. 

Keywords

• AISI 4140,AISI 4340,martenzit hacim oranı,mekanik özellikler

Investigation on Fracture Toughness Values for Various Martensite Volume Fractions

Abstract

In this study the effect of martensite volume fraction on hardness and fracture toughness properties of AISI 4140 and AISI 4340 steels were investigated. After determining of intercritical boundary temperatures for steels, the water quenching processes were performed at three intercritical annealing temperatures. The martensite volume fractions were determined from microstructure images for each condition by using image processing method. The martensite volume fraction increased with increasing intercritical temperature. The hardness and fracture toughness tests were conducted on the specimens. Increasing of martensite content increased the hardness values whereas decreased the fracture toughness values. Although AISI 4340 had higher hardness than AISI 4140, it had lower fracture toughness properties.

Keywords

• AISI 4140,AISI 4340,martensite volume fraction,mechanical properties

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