Browsing by Author "Gunen, Ali"

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A Comparative Study on Experimental and FEA-Based Simulation of Dry Sliding Wear Behavior of Boronized AISI 304 Stainless Steel at Elevated Temperatures
(Pleiades Publishing Ltd, 2025) Gok, Mustafa Sabri; Kucuk, Yilmaz; Khosravi, Farshid; Gunen, Ali; Karakas, Mustafa Serdar; Guden, Mustafa
In this study, the influence of boronizing on the high-temperature wear behavior of AISI 304 was examined experimentally and with FEA simulation. Boronizing, conducted at 950 degrees C for 3 h using the powder-pack boronizing technique, showed an approximately 7-fold increase in hardness compared to untreated sample. Boride layer characterization was performed using XRD, SEM, and EDS line analyses. Wear tests were performed at ambient temperatures of 25, 250, and 500 degrees C. While the wear rates of the untreated sample increased dramatically with increasing temperature, those of the boronized samples were significantly limited. FEA simulation using the Johnson-Cook fracture model demonstrated a high degree of consistency with the experimental wear profiles and this alignment enables reliable wear predictions. The oxide layer formation was observed on the worn surface of boronized samples during the tests at elevated temperatures, resulting in less plastic deformation.
Effect of Vibratory Peening Pretreatment on Boriding Kinetics of Hadfield Steel by Taylor Expansion Model
(Elsevier Science S.A., 2025) Gunen, Ali; Lindner, Thomas; Karakas, Mustafa Serdar; Unal, Okan; Keddam, Mourad; Malachowska, Aleksandra; Lampke, Thomas
X120Mn12 high-manganese steel is widely used for its excellent toughness, yet its limited wear resistance under low-impact conditions necessitates surface enhancement. While boronizing improves surface hardness, the role of vibratory peening pretreatment (VPP) in influencing boride layer growth remains underexplored. In this study, the influence of VPP on the boronizing kinetics of X120Mn12 austenitic manganese steel was systematically evaluated. VPP was conducted at 50 Hz with a 5 mm amplitude, using 3 mm diameter AISI 52100 bearing balls (approximate to 58 HRC) for 2 h. Subsequent pack boronizing was performed at temperatures of 1023 K, 1173 K, and 1323 K for durations of 1, 3, and 5 h. Microstructural analysis revealed that peening induced significant near-surface plastic deformation to a depth of approximately 150 mu m, resulting in a 12 % reduction in grain size and a two-fold increase in surface hardness. The boride layer thickness ranged from 13.63 to 193.15 mu m, with microhardness values ranging from 984 to 1741 HV0.1 in peened specimens, compared to 11.89-180.89 mu m and 898-1720 HV0.1 in the as-cast counterparts. Enhanced dislocation density and vacancy formation decreased the boron activation energy, which was determined using a Taylor-expansion diffusion model, yielding values of 150.53 kJ center dot mol- 1 for the peened samples and 155.72 kJ center dot mol- 1 for the as-cast samples. These findings demonstrate that VPP effectively refines the microstructure and accelerates boron diffusion by generating high-density defect structures.