Hakan Gaşan

Effect of Different Surface Treatment Methods on the Friction and Wear Behavior of AISI 4140 Steel

In this study, the effects of various surface treatments on the friction and wear behavior of AISI 4140 steel have been evaluated. Sample surfaces of AISI 4140 steel were treated by quenching, carburizing, boronizing and plasma transferred arc (PTA) modification. The microstructural characteristics of surface treated steel samples were examined by optical microscopy and scanning electron microscopy (SEM). The mechanical properties of the samples including the surface roughness, microhardness, and abrasive and adhesive wear characteristics were also evaluated. Wear tests were applied by using a block-on-disc configuration under dry sliding conditions. The wear behavior and friction characteristics of the samples were determined as a function of sliding distance. Each sample group was compared with the other sample groups, and it was observed that the carburized samples demonstrated the lowest weight losses; however, PTA-treated samples demonstrated the lowest coefficient of friction in comparison to the other sample groups at the same sliding distance.

Particle Size Distribution and Shape Characterization of the Chips Produced During Granite Machining in Relation to Process Forces and Specific Energy

The objective of the present work was to characterize the particle size/size distribution and shape of the chips produced during granite machining in relation to process forces and specific energy. To achieve this goal, two different series of circular sawing experiments were performed on an instrumented full-scale rig. The first series of sawing tests was carried out with a newly dressed blade, while the second series of tests were carried out at a relatively worn state. For each case, cutting forces and specific energy values were determined. By using a computer image-processing system, size and shape descriptors of the collected chips from the cutting debris of both series of tests were quantitatively evaluated. The results of the analyses showed that the size/size distributions of the produced chips were greatly influenced by the wear state of the diamond segments. Size/size distribution characteristics of the chips were also found to correlate with the force ratio and specific energy, indicating that particle size analysis of the cutting debris could be used as an efficient guide to sawing efficiency in industrial applications. Despite to diversity in their size/size distribution characteristics, the chips produced in both series of sawing tests showed quite similar shape characteristics.

Boride Layer Growth Kinetics of the Borided Hypoeutectoid Plain Carbon Steels by the Powder-Pack Method

Abstract In the present work, kinetics of boriding of hypoeutectoid plain carbon steels has been studied. Boriding of the AISI 1010, 1020, 1040 and 1060 test materials has been performed by means of a powder-pack method using EKabor 2 ® powders. Boriding heat treatments were performed at 1173 K, 1223 K, 1273 K and 1323 K for 2, 4 and 6 h. The borided materials were characterised by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and optical microscopy in order to determine the phase contents (FeB and Fe2B). Boride layer thickness was determined by optical microscopy and hardness by microhardness testing. The thickness of borided layers measured ranged from 71 to 362 μm. It was found that the effect of boriding time and temperature on the increasing boride layer thickness was more significant than the effect of increasing the carbon content. The hardness of the boride layers ranged from 1243 to 1740 HV. The kinetics of the reactions, K=K0exp(-Q/RT), were determined by varying the boriding temperature and time for the materials. A correlation between the C content and activation energy has been established by this study.