Person: TUTAR, MÜMİN
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TUTAR
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MÜMİN
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Publication The effect of duplex surface treatment on erosion performance of qro 90 supreme steel(Springer India, 2019-04-01) Tutar, Mumin; TUTAR, MÜMİN; Aydın, Hakan; Durmus, Ali; DURMUŞ, ALİ; AYDIN, HAKAN; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0002-7286-3433; 0000-0001-7364-6281; 0000-0002-5037-1120; J-2753-2016In this study, CrN and TiAlN thin films were deposited on plasma-nitrided QRO 90 Supreme hot work tool steel by physical vapor deposition process and analysed with regard to their erosion performance under hydro-abrasive erosion conditions. The as-received specimens were quenched to room temperature from 1050A degrees C and tempered gradually at 605A degrees C for 2 h and at 560A degrees C for 4 h. These specimens were plasma-nitrided for 10 h at 500A degrees C at a pressure of 250 Pa in a gas mixture of 80% N-2 + 20% H-2 and then coated with TiAlN or CrN coatings by cathode arc evaporation. The specimens were characterized by metallographic techniques, SEM, EDS and micro-hardness test. Plasma nitriding and duplex surface treatments significantly increased the hardness of the specimens and thus significantly reduced the erosion of the specimens. The hardnesses on the surface of plasma-nitrided, CrN-deposited and TiAlN-deposited QRO 90 steels were 1092 HV0.025, 2436 HV0.025 and 3578 HV0.025, respectively. TiAlN-coated specimens were about 17-fold harder than the as-received specimens and over 3-fold harder than the plasma-nitrided specimens. The erosion resistance of CrN-coated specimens was increased by a factor of 3.6 and 1.5 compared with that of the as-received and plasma-nitrided specimens, respectively. A brittle fracture phenomenon was observed on the eroded surface of the duplex-treated specimens while a ductile material removal was observed on the as-received and the tempered specimens. The plasma-nitrided specimens showed a mixed behaviour of ductility and brittleness.Publication The optimisation of welding parameters for electrical resistance spot-welded twip steels using a taguchi method(Pamukkale Üniversitesi, 2018-01-01) Tutar, Mümin; Aydın, Hakan; Bayram, Ali; TUTAR, MÜMİN; AYDIN, HAKAN; BAYRAM, ALİ; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0002-7286-3433; 0000-0001-7364-6281; J-2753-2016; JQB-9181-2023; GZC-1297-2022The aim of this work is to optimize the welding parameters of electrical resistance spot welded TWIP steel sheets using a Taguchi method. The welding parameters, such as weld current, welding time and electrode force, were determined according to the Taguchi orthogonal array L9 using a randomized approach. The optimum welding parameters for the peak tensile shear load of the joints were predicted, and the individual importance of each parameter on the tensile shear load of the resistance spot weld was evaluated by examining the signal-to-noise (S/N) ratio and analysis of variance (ANOVA). The optimum weld current, welding time and electrode force were found to be 12 kA, 300 ms and 3000 N, respectively. The ANOVA results indicated that the weld current has the highest statistical effect with 78.73% on the tensile shear load, followed by the welding time and electrode force. The tensile shear load of the resistance spot welding joints increased with increasing weld current and electrode force. But, higher welding time led to relatively lower tensile shear load. In addition, the fracture surface characterization of the selected joints was conducted using scanning electron microscopy (SEM) technique. In this examination, it has been found that the joints having higher weld strength exhibited a relatively more ductile fracture characteristic.