Effect of chill formation on the mechanical properties and microstructure of grey and nodular cast irons used in automotive industry
Journal Name:
- Pamukkale Üniversitesi Mühendislik Bilimleri Dergisi
Keywords (Original Language):
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Abstract (2. Language):
Cam shafts used in automobiles are produced by cast iron (grey cast iron, nodular cast iron) or steel. In this study, effect of chill formation on the surface of grey and nodular cast irons is investigated on the wear behavior, hardness, impact toughness and microstructure of grey and nodular cast irons. For this purpose, four types cam shaft made of grey cast iron with and without chill on the surfaces and nodular cast iron with and without chill on the surfaces, were casted. Mechanical tests were conducted after the camshafts have been produced by casting method. Surface hardness and wear resistance of grey and nodular cast irons have been improved by chill formation on the surfaces and it is concluded that the amount of wear on the surfaces of grey cast iron with chill and nodular cast iron with chill is almost the same. Maximum hardness value was obtained on the surface of grey cast iron with chill. The impact toughness has been found to decrease by chill formation. Maximum impact toughness value was obtained on nodular cast iron. Microstructures of grey cast iron with and without chill and nodular cast iron with and without chill were examined under optical microscope and worn surfaces of cast irons were examined by scanning electron microscopy (SEM). Wear mechanisms of the four types of cast iron were evaluated by SEM examination.
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Abstract (Original Language):
Otomobillerde kullanılan kam milleri dökme demirden (gri dökme demir, küresel dökme demir) veya çelikten üretilmektedir. Bu çalışmada gri ve küresel grafitli dökme demirin yüzeylerinde çil oluşumunun sertlik, aşınma, darbe tokluğu ve mikro yapı üzerine etkisi incelenmiştir. Bu amaçla, gri ve küresel dökme demirlerden çilli ve çilsiz olmak üzere dört farklı kam mili hazırlanmıştır. Kam milleri döküm yöntemiyle üretildikten sonra mekanik testler yapılmıştır. Yüzeyde oluşan çilin dökme demirin sertliğini ve aşınma direncini artırdığı, gri çil ve küresel çil dökme demirin aşınma miktarının hemen hemen aynı olduğu tespit edilmiştir. Maksimum sertlik gri çil dökme demirde elde edilmiştir. Gerçekleştirilen darbe tokluğu testi sonucunda darbe tokluğunun çil oluşumu ile azaldığı tespit edilmiştir. Maksimum darbe tokluğu Küresel dökme demirde elde edilmiştir. Dökme demirlere ait mikro yapı optik mikroskopta incelendi ve aşınma yüzeyleri ise taramalı elektron mikroskobu ile incelenerek aşınma mekanizmaları değerlendirildi.
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