Wire-EDM performance and surface integrity of Inconel 718 with unique microstructural features fabricated by laser powder bed fusion

The version of record of this article, first published in International Journal of Advanced Manufacturing Technology, is available online at Publisher’s website: https://doi.org/10.1007/s00170-023-12924-7.Inconel 718 alloy is difficult to machine using conventional methods due to its physical properties. Thereby, additive manufacturing (AM) of IN718 components with near-net shapes has been extensively studied. Even though AM processes provide shape and size accuracy, there is still the need for the machining of the AM-processed components to achieve the final shape of a component. Laser powder bed fusion (LPBF) has been successfully utilized to fabricate near-net shape IN718 components; moreover, the microstructure of LPBF-IN718 was unique owing to the AM processing, resulting in differences in grain size, grain boundary characteristics, and grain orientations. Furthermore, these microstructural characteristics are expected to alter the machining performance of IN718. Therefore, this study investigated the wire electro-discharge machining (WEDM) performance of LPBF-718 samples compared to wrought IN718 while focusing on the unique microstructure characteristics of LPBF-IN718 samples (lamella, single-crystal, ploy-crystal). Three different cutting strategies (rough, semi-finish, and finish) were implemented to understand the performance of the multi-pass cutting phenomenon and its effect on the surface of IN718. For all samples, rough (single pass) cutting displayed high roughness, while finish (three passes) cutting exhibited good surface quality. Compositional analyses on the machined surface showed debris formation including Zn and Cu-containing recast material, indicating wire erosion. The surface of single-crystal LPBF-IN718 after the WEDM process was smooth owing to its large grain size and less amount of grain boundary, resulting in slow cutting speed but a good surface finish. Thus, this study, for the first time, investigated the effect of unique microstructural characteristics of LPBF-fabricated IN718 on WEDM performance and machined surface quality

Effect of the cooling in the austempering process on the abrasive wear behaviour of austempered ductile iron

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.In this study, ductile iron was austenised at 900 oC for 1 h and austempered at 400 0C for 2 h in single step austempering process, whereas it was austenised at 900 oC for 1 h and immediately quenched in a salt bath at 400 oC for 10 minutes and then the temperature of bath was decreased by 1.88 oC per minutes down to 250 oC 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

Effect of the matrix structure on the friction coefficient and pin tempureture of ductile iron under dry sliding conditions

Bu çalışmada, matris yapısının küresel grafitli dökme demirin (KGDD) aşınma davranışına, aşınma sırasında oluşan sürtünme katsayısına ve pim sıcaklığına etkisi araştırılmıştır. Aşınma testleri disk üzerinde pim türü cihazda, 1 m s-1 kayma hızında, 20, 40 ve 60 N yük ve 3,6 km kayma mesafesinde, normal atmosfer şartlarında ve oda sıcaklığında gerçekleştirilmiştir. Aşınma yüzeyleri tarama elektron mikroskobu (SEM) ile incelenmiştir. Uygulanan yükün artmasına bağlı olarak döküm durumu ferritik KGDD’in aşınma hızı artarken, döküm durumu perlitik KGDD numunenin aşınma hızı azalmaktadır. Testler, döküm durumu perlitik KGDD’nin sürtünme katsayısı ve sürtünme sıcaklığının, döküm durumu ferritik KGDD’den daha yüksek olduğunu göstermiştir. Deneysel sonuçlar, döküm durumu perlitik ve ferritik KGDD’lerin sürtünme katsayısının azalmasıyla, sürtünme sıcaklığının arttığını ortaya koymaktadır.In this study, the effect of the matrix structure on the dry sliding wear behaviour, friction coefficient and pin temperature of ductile irons was investigated. Wear tests were carried out at normal atmospheric conditions and room temperature on a pin on disc type tester at constant sliding speed (1ms-1) and sliding distance (3.6 km) under various sliding loads in a range of 20 to 60 N. The worn surfaces were examined by scanning electron microscopy (SEM). Wear rate of as-cast ferritic ductile irons increased with increasing test load, whilst that of as-cast pearlitic irons decreased. Tests revealed that, as-cast pearlitic ductile iron exhibited higher friction coefficient and friction temperature than as-cast ferritic ductile iron. The experimental results showed that the friction temperature increased with decreasing the friction coefficient of as-cast ferritic and pearlitic ductile irons

Investigation of seasonal variations and sources of atmospheric polychlorinated naphthalenes (PCNs) in an urban area

Atmospheric concentrations of 32 polychlorinated naphthalene (PCN) congeners were determined at four sites (i.e., Suburban, Urban 1, Urban 2, and Industrial) in Izmir, Turkey and their possible sources were investigated. Total PCN (Sigma 32PCN) concentrations ranged between 5.2 (Suburban 1) to 162 pg m(-3) (Urban 1) in summer, while in winter, they ranged from 3.7 (Suburban) to 229 pg m-3 (Urban 1). PCN-24/14 was the dominant congener at all sites (contributing 12-27% to Sigma(32)PCNs), followed by PCN-33/34/37, PCN-28/43, PCN-17/25, PCN-23 and PCN-19. Investigation of possible sources indicated that the combustion processes also contribute substantially to atmospheric PCN concentrations in addition to emissions from sources related to historical use of technical mixtures. (C) Author(s) 2012. This work is distributed under the Creative Commons Attribution 3.0 License