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In this study, the effects of cutting speed, milling direction (down milling, up milling), coating layer (TiAlN and TiAlN-TiN) and the number of inserts of tool holder on the surface roughness and tool life in dry milling of Inconel 718 superalloy were investigated. In the first place, the effects of control factors on the tool life were studied at the cutting speeds of v = 50 m/min and v = 100 m/min. The alternation of flank wear depending on the cutting time was examined. The types of wear and wear mechanisms were determined by examining the optical images of worn tools. In the second part of the study, for the purpose of investigating the effects of control factors on the surface roughness, L16 Taguchi Technique was used and the optimal control factor levels, giving the lowest value of the average surface roughness parameter (Ra) were determined. The effect of cutting speed on the tool life was more than the effects of the milling type and number of inserts. Down milling resulted in longer tool life compared to up milling method. In up milling, longer tool life was obtained with 2 inserts at low cutting speeds and with 4 inserts at high cutting speeds. TiAlN- TiN coated tools exhibited twice as long tool life than the TiAlN coated tools. For both milling methods, the most effective wear types were flank wear and nose wear.

Bu çalışmada, Ç1050 ve Ç4140 çeliklerinin kaplamasız ve kaplamalı seramik kesici takımlarla işlenmesinde, kesme parametreleri ile iş parçası ve takım sertliklerinin, takım ömrü ve takım aşınması üzerindeki etkileri araştırılmıştır. Taguchi Tekniği kullanılarak en yüksek takım ömrü değerlerini veren optimum kontrol faktörleri belirlenmiştir. Tahminsel takım ömrü denklemleri çıkartılmıştır. Ayrıca, aşınmış uçların SEM görüntüleri incelenerek takım aşınma tipleri belirlenmiştir. Deneysel sonuçlar, sırasıyla iş parçası sertliği, kesme hızı, kesme hızı-ilerleme miktarı etkileşimi, kesme hızı-iş parçası sertliği etkileşimi, talaş derinliği-kesici takım sertliği etkileşimi, ilerleme miktarı-iş parçası sertliği etkileşimi ve ilerleme miktarının takım ömrü üzerinde en etkili faktörler olduğunu göstermiştir. Faktör etkileşimlerinin yer aldığı ikinci dereceden tahminsel denklem daha güvenilir sonuçlar vermiştir. Ç1050 ve Ç4140 çeliklerinin seramik takımlarla işlenmesinde çentik, yan kenar ve krater aşınması gözlenmiştir. In this study, the effects of cutting parameters and the effects of workpiece hardness and tool hardness on tool life and tool wear have been investigated in machining of AISI1050 and AISI4140 steels by uncoated and coated ceramic cutting tools. Optimum cutting conditions for maximum tool life were determined using the Taguchi technique. Predictive tool life equations were derived. In addition, types of tool wear were observed by shown worn surfaces with a scanning electron microscope (SEM). The results indicated that the workpiece hardness, cutting speed, cutting speed-feed rate interaction, cutting speed-workpiece hardness interaction, dept of cut-cutting tool hardness interaction, feed rate-workpiece hardness interaction and feed rate were found out to be the most effective factors among control factors on tool life. It is observed that the second order predictive equation provided more reliable results. In machining AISI1050 and AISI4140 steels, notch wear, flank wear and crater wear observed on ceramic tools. Gazi Üniversitesi TEF-07/2003-38

The surface roughness model was developed in terms of main cutting parameters such as cutting speed, feed rate and depth of cut, using response surface methodology. Machining tests were carried out in turning AISI 1050 hardened steels by cubic boron nitride (CBN) cutting tools under different conditions. The model predicting equations for surface roughness of R-a, R-z, and R-max were developed using an experimental data when machining steels. The results indicate that the feed rate was found out to be dominant factor on the surface roughness, but it decreased with decreasing cutting speed, feed rate, depth of cut for these tools. In addition, average surface finish of Ra value produced by CBN cutting tool was about 0.823 mu m when machining hardened steels. However, the Ra value decreased about 0.55 mu m in terms of trial conditions. Moreover, a good agreement between the predicted and experimental surface roughness was observed within reasonable limit. (C) 2007 Elsevier Ltd. All rights reserved.