Osman Nuri Çelik

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.

Effect of Nano Hexagonal Boron Nitride Lubricant Additives on the Friction and Wear Properties of AISI 4140 Steel

The aim of this study was to investigate the effects of nano hexagonal boron nitride(hBN) particles on the friction and wear properties of AISI 4140 steel material when the hBN particles are used as an oil additive. Nano hexagonal boron nitride powders, which were produced using a special process, were dispersed in engine oil (SAE10 W) to enhance lubrication. The amount of nano hexagonal boron nitride in the engine oil was varied from 0 to 10% by volume, and four different lubricant samples were prepared. Wear tests were conducted using ball-on-disc geometry. The worn surfaces of substrates were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The experiments showed that the nano hexagonal boron nitride particles that were used as an oil additive affected the friction and wear behavior. A 14.4% improvement in the friction coefficient and a 65% decrease in the wear rate were achieved through the use of the nano hBN as an oil additive.

Microstructure and Wear Behavior of TIG Surface-Alloyed AISI 4140 Steel

In this study, AISI 4140 steel surfaces were alloyed with preplaced SiC/C powders using a tungsten–inert gas (TIG) heat source. The effects of different production parameters on the microstructure, hardness, and wear resistance of the alloyed surfaces were investigated. Following the surface alloying, conventional characterization techniques such as optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to study the microstructure of the alloyed surfaces. Hardness measurements were performed across the alloyed zones, and wear properties of the alloyed surfaces were evaluated using a block-on-disc wear test method. The collected data suggest that alloyed zones solidify into different microstructures depending on the production parameters. The alloyed surfaces exhibited an increase in hardness and wear resistance; this was attributed to the presence of harder phases and graphite. Lamellar or layered crystal structures of graphite have good lubricity and decrease coefficient of friction. Hardness values of the alloyed surfaces varied between 670 and 1165 HV. The minimum mass loss was observed in the sample that was alloyed with a 0.0581 cm/s process speed, 0.5/0.2 g/s powder feed rate, and a 29.1 kJ/cm heat input. The exhibited mass loss ratio was attributed to M3C, M7C3, and FeSiC carbides in the microstructure. The results conclude that TIG can be used effectively for surface alloying with SiC/C powders to improve the wear resistance of the AISI 4140 steel surface.

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.

Wear Characteristics of Traditional Manganese Phosphate and Composite hBN Coatings

In this study, the tribological properties of traditional manganese phosphate coatings and composite hBN coatings composed of nano-hexagonal boron nitride (hBN) in layered manganese phosphate crystals on AISI 1040 steel were investigated. Wear tests were carried out under controlled temperature and humidity using ball-on-disc tribometers for samples that were either submerged in oil or retaining oil on their surfaces at a sliding speed of 2.5 cm/s with loads of 1, 3, 5, and 10 N and sliding distances of 40, 80, 100, and 120 m. The surface profiles before and after the tests were used to characterize the wear. The surfaces of the coated samples were examined using scanning electron microscopy (SEM). The coefficients of friction and wear rates of the coated samples were also measured. The average wear rates of the composite hBN-coated samples were significantly lower than those of the traditional manganese phosphate–coated samples for each of the loading conditions for the oil submersion and retained oil tests. The coefficient of friction (COF) values for the traditional manganese phosphate–coated samples did not change significantly with increasing load. The COF values for the composite hBN coated–samples decreased with increasing load in the oil submersion test.

Modeling and analysis of the effects of nano-oil additives on wear properties of AISI 4140 steel material using mixture design

The aim of this study is to investigate the effects of nano-oil additives on the wear properties of AISI 4140 steel material. This paper also introduces an application of mixture design to the development of a new proportion formulation for nano-oil additives dispersed in engine oil (SAE10W) to enhance lubrication. A mixture design procedure was performed on the basis of design, modeling, optimization, and confirmation steps. Based on a simplex lattice design, a cubic model was established as a function of the nanoparticle fractions. The optimal proportions were obtained by considering the cross-sectional area of the wear profile. A 77.81% decrease compared to the base oil was obtained by using ZnO and carbon nanotubes.

Effect of Isothermal Bainitic Quenching on Rail Steel Impact Strength and Wear Resistance

The effect of heat treatment regimes on hardness, impact strength, and wear resistance of rail steel for high-speed tracks (rail quality category R350HT) is studied. Analysis of steel properties with a different structure is compared: pearlitic, and upper and lower bainite. It is shown that the steel with bainitic structure has the best impact strength, but wear resistance is better for steel with a lower bainite structure.