ÖSTEMPERLENMİŞ KÜRESEL GRAFİTLİ DÖKME DEMİRİN ABRASİV AŞINMA DAVRANIŞINA ÖSTEMPERLEME İŞLEMİNDE SOĞUTMANIN ETKİSİ

Öz

Bu çalışmada, geleneksel tek kademeli östemperleme işleminde, küresel grafitli dökme demir (KGDD) numuneler 900oC’de 1 saat östenitlenmiş, müteakiben tuz banyosunda 400oC’de 2 saat östemperlenmiştir. İkikademeli östemperleme prosesinde ise KGDD numuneler 900oC de 1 saat östenitlendikten sonra derhal 400oC’lik tuz banyosuna aktarılmış, 10 dakika bu sıcaklıkta bekletildikten sonra banyonun sıcaklığı 1.88oC/dak hızla 250oC’a soğutulmuştur. Geleneksel tek kademeli östemperleme prosesi ile üretilen üst ösferritik ve ikikademeli prosesle üretilen üst ve alt ösferritik Östemperlenmiş Küresel Grafitli Dökme Demir (ÖKGDD) numunelerin abrasiv aşınma deneyleri, disk üzerinde pim cihazında 10, 20 ve 30 N normal yük altında, 180 mesh (80 μm) boyuta sahip Al2O3 zımpara üzerinde gerçekleştirilmiştir. İki kademeli östemperleme prosesiyle üretilen küresel grafitli dökme demirin sertliği, tek kademeli prosesle üretilen dökme demirinkinden daha yüksek olmasına rağmen, her iki dökme demirin benzer abrasiv aşınma davranışı sergilediği görülmüştür. Ayrıca iki kademeli östemperlenmiş küresel grafitli dökme demirde abrasiv aşınma direnci uygulanan yükün artmasıyla artmıştır.

Anahtar Kelimeler

• Abrasive aşınma, östemperlenmiş küresel grafitli dökme demir, sertlik, mikroyapı.

EFFECT OF THE COOLING IN THE AUSTEMPERING PROCESS ON THE ABRASIVE WEAR BEHAVIOR OF AUSTEMPERED DUCTILE IRON

Öz

In this study, ductile iron was austenised at 900 o C for 1 h and austempered at 400 0 C for 2 h in single step austempering process, whereas it was austenised at 900 o C for 1 h and immediately quenched in a salt bath at 400 o C for 10 minutes and then the temperature of bath was decreased by 1.88 o C per minutes down to 250 o C in two-step austempering process. The upper ausferritic austempered ductile iron (ADI) specimens produced by conventional single step austempering process and the upper and lower ausferritic specimens produced by twostep austempering process were abraded on the pin on disc apparatus under the normal load of 10, 20, 30 N, by rubbing the specimens on abrasive Al2O3 grains with diameters of 180 Mesh (80 µm). Although the ductile iron austempered in two steps had higher hardness than the ductile iron austempered in single step, they showed similar abrasive wear behavior. In addition, the abrasive wear resistance of two step austempered specimen increased with increasing applied load.

Anahtar Kelimeler

• Abrasive wear,austempered ductile iron,hardness,microstructure

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