This study presents the impact of molybdenum (Mo) inclusion on microstructure, mechanical, and machinability behavior of steels manufactured with powder metallurgy (PM) approach. PM steel samples with different molybdenum ratios were pressed at 750-MPa pressing pressure and sintered in the atmosphere-controlled tube furnace at 1400°C for 1 h. While particle size and distribution of phases of PM steels with different molybdenum ratios were determined by optical microscope, mechanical properties were determined by applying tensile test. The results were observed that 3% Mo weight-added steel displayed the maximum yield and tensile strength. In addition, the machinability properties of 3% Mo-added steel, which has the highest yield and tensile strength, were investigated. In this work, we researched the thrust force and surface roughness as machinability output, and drilling parameters on the output were determined by utilizing analysis of variance. Finally, SEM images were taken from the inner surfaces of the machined holes and the fractured surfaces from tensile test, and information about the machinability of this alloy produced with PM was presented. As a result, an increase in yield and tensile strength and a reduction in strain were identified with the increase in Mo content. Moreover, the coated cutting tools are better on the machining output than the uncoated cutting tools in terms of green environment. The most important factors on the Fz and Ra are the coating condition and the feed rate with 56.53% and 43.62% PCR, respectively.

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This study focused on the influences of drilling parameters on hole quality and thrust force in drilling of carbon fiberreinforced polymer (CFRP) composite laminates via variable feed rate. Drilling experiments were carried out by using three different cutting speeds, feed rates and the qualities of tungsten carbide drill. Scanning electron microscopy and coordinate measurement machine were used for hole surface damage and diameter analyses, and also a portable instrument and 3D optical profilometer were utilized for surface roughness measurement. It was identified that thrust force (F z), delamination factor (F d) and average surface roughness (R a) values attained in drilling processes by variable feed rate are lower than those of constant feed rate with average of 14%, 3% and 18%, respectively. Besides, the hole diameter (D) values obtained with variable feed rate in hole exit were higher than those of constant feed rate. Moreover, the higher F z values were obtained with diamond-coated and TiAlN-coated drills than those of uncoated drill with 55% and 77%, respectively. The interactive influences of drilling parameters on machinability factors were evaluated via analysis of variance, and then, the most significant parameter was specified as the feed rate for F d , just as the drill quality for F z , R a and D. According to the experimental and statistical results, we suggested that the novel drilling strategy is a significant alternative for the step hole and conventional drilling of CFRP laminates.

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Bu çalışmada, ergiyik yığma modelleme (FDM) esaslı 3D yazıcı kullanılarak üretilen PLA+ numunelerin mekanik özelliklerine baskı hızı, doluluk oranı ve tarama açısının etkileri detaylı olarak araştırılmıştır. Bu amaçla, Taguchi L18 deney tasarımına göre 3D yazıcı ile standart çekme test numuneleri hazırlanmıştır. İşlem parametrelerinin (Baskı hızı, doluluk oranı ve tarama açısı) çekme dayanımı üzerindeki etkileri varyans analizi (ANOVA) ile belirlenmiştir. Ayrıca, Taguchi metodolojisi uygulanarak çekme dayanımı için işlem parametrelerinin optimizasyonu yapılmıştır. Sonuç olarak, çekme dayanımı üzerinde en etkin parametre doluluk oranı olurken, sırasıyla tarama açısı ve baskı hızı diğer önemli parametreler olarak tespit edilmiştir.

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