Yasar Totik

The effects of induction hardening on wear properties of AISI 4140 steel in dry sliding conditions

Wear behaviour of induction hardened AISI 4140 steel was evaluated under dry sliding conditions. Specimens were induction hardened at 1000 Hz for 6, 10, 14, 18, 27 s, respectively, in the inductor which was a three-turn coil with a coupling distance of 2.8 mm. Normalised and induction hardened specimens were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy and X-ray diffraction. The wear tests using a pin-on-disc machine showed that the induction hardening treatments improved the wear behaviour of AISI 4140 steel specimens compared to normalised AISI 4140 steel as a result of residual stresses and hardened surfaces. The wear coefficients in normalised specimens are greater than that in the induction hardened samples. The lowest coefficient of the friction was obtained in specimens induction-hardened at 875 °C for 27 s.

The effects of artificial aging on wear properties of AA 6063 alloy

Abstract Wear behaviour of age-hardened 6063 aluminium alloy was evaluated under dry sliding conditions. A certain part of the aluminium samples was solution treated at 510 °C for 2, 4, 6 and 8 h, water-quenched then aged at 180 °C for 4 h, and the other part was solution treated at 510 °C for 6 h, water-quenched then aged at 180 °C for 1, 2, 3, 4 and 5 h in a muffle furnace. The as-cast and the aged samples were fully characterised before and after the wear testing using hardness, profilometer, scanning electron microscopy (SEM), optical microscopy, X-ray diffraction, and energy dispersive detector (EDS). The wear tests using on a pin-on-disc machine showed that the aging treatments improved the wear behaviour of AA 6063 alloy compared to as-cast samples.

The effect of homogenization treatment on the hot workability between the surface and the center of AA 2014 ingots

This paper discusses an investigation of the structural and mechanical properties between the surface and the center of AA 2014 alloy ingots obtained by direct casting, and achievement of uniform workability by applying a homogenization treatment. Ingots 200 mm in diameter were homogenized; then, the structural and mechanical properties of samples taken from four different regions of the ingots between the surface and the center were determined using hot torsion and hardness tests, light optical microscopy, and X-ray diffraction (XRD). Hot torsion tests after homogenization were conducted at a deformation temperature of 440 deg. C with a strain rate of 2x10{sup -2} s{sup -1}. The peak stress and the strain difference between the surface and the center decreased with the homogenization treatment. The least difference between the surface and the center was obtained from the ingot sections cooled in the furnace from a homogenization temperature of 510 deg. C based upon hot torsion test at a temperature of 440 deg. C.

CHARACTERIZATION OF TiB2 COATING ADHERENCE BY A MULTI-PASS SCRATCH TESTING

TiB2 films deposited using various deposition techniques are used to increase the wear lifetime of industrial components. The performance of TiB2 films is dependent on the coating–substrate adhesion. In this study, the fatigue behavior of TiB2 films was investigated using the multi-mode scratch method. Films of TiB2 were deposited on silicon wafers and AISI M2 steel substrates at different frequencies by pulsed-dc closed field unbalanced magnetron sputtering (CFUBMS). The microstructures of the films were investigated using SEM techniques, and the hardness was measured using a microhardness tester. A multi-mode operation was used for sliding-fatigue, like multi-pass scratching in the same track at different fractions of critical load (bidirectional sliding) and a standard mode using progressive load operation. It was observed that the films deposited at low frequencies had higher adhesion strength and microhardness, and a denser microstructure.

An investigation of the relationship between heat treatment and microstructure in (TiAlV)N and (TiAl)N ceramic films

(TiAl)N and (TiAlV)N films coated on M2 high-speed tool steel were heat-treated in an argon atmosphere at temperatures of 700°C, 800°C and 900°C for 3 h. The structural and mechanical properties of the ceramic films were examined by microindentation hardness testing, X-ray diffraction (XRD) and scanning electron microscopy. Annealing at elevated temperatures led to a decrease in the hardness of the ceramic films. The magnitude of this hardness change became larger with increasing annealing temperature. Elevated temperature anneals also modified the distribution of elements in the ceramic films. XRD data show that phase transformations take place in the structure. These transformations resulted in a decrease in the hardness, residual stress and spacing between the planes of the film. The surface topography was not affected by the heat treatment.

The effect of plasma electrolytic oxidation process parameters on the tribocorrosion properties of TiO2 coatings

Abstract Despite the fact that Titanium and its alloys are materials which have excellent corrosion-resistant properties, they have poor wear and friction performance under tribological conditions. The aim of this study is to find suitable parameters for the surface treatment of Cp-Ti substrates which are used under saline environment. In this study, TiO2 coatings were grown on Cp-Ti substrates at different frequencies which are parameters of the coating process. Due to its low cost and ability to achieve high thicknesses, The Plasma Electrolytic Oxidation (PEO) method was applied to grow TiO2 coatings. The microstructures, morphology, and crystallographic structure were analyzed using SEM and XRD. Tribocorrosion properties of the coatings were investigated using a combination of the pin-on-disk wear test and potentiodynamic polarization test units. The frequency is known to have a strong impact on the PEO process. The impacts of frequency changes on the PEO coating performance were examined under a constant voltage. As result, the increase of the frequency caused smaller pores and cracks in the surface morphology of the coating and at the same time this yielded an increment on the tribocorrosion behavior of the coating.

The investigation of adhesion and fatigue properties of TiN/TaN multilayer coatings

Abstract TiN/TaN multilayer coatings exhibit excellent mechanical properties when compared to single layer nitride coatings. In this study, TiN/TaN multilayer coatings were deposited on Mo-alloy and W-alloy substrates by CFUBMS. The structural and mechanical properties of coatings were analysed using XRD, EDS, SEM and a micro-hardness tester, respectively. To determine the adhesion and fatigue behaviour of the coatings were performed a scratch test in two modes that a standard mode with progressive loading and sliding-fatigue multimode operation with unidirectional sliding, respectively. A microscope was used to characterize adhesion and fatigue failures. The structural, mechanical, adhesion and fatigue properties of TiN/TaN multilayer coatings significantly changed depending on the substrate.

Analysis of Tribo-corrosion Properties of MAO/DLC Coatings Using a Duplex Process on Ti6Al4V Alloys

In recent years, various technologies have been increasingly investigated for the surface modification of Ti and Ti alloys. Microarc oxidation (MAO) is one of the effective techniques to improve surface properties. However, it has some disadvantages for sliding wear applications and/or aggressive environments. In this study, the combined MAO and closed field unbalanced magnetron sputtering process was used to deposit duplex MAO/diamond-like carbon (DLC) coatings on Ti6Al4V alloy. Analysis of the microstructures, morphology, and crystallographic structure were performed by using a SEM, Raman, and XRD. The wear, corrosion, and tribo-corrosion properties of the coatings were investigated using the pin-on-disk wear test, potentiodynamic polarization test, and combining tribo-corrosion test unit, respectively. The results of this study have shown that duplex MAO/DLC coatings exhibit better wear, corrosion, and tribo-corrosion properties than the DLC or MAO monolayer on Ti6Al4V alloy substrate. MAO/DLC coatings exhibited dense structure, lower coefficient of friction and corrosion current density, and higher tribo-corrosion resistance. The results have also shown that MAO/DLC duplex coatings on Ti6Al4V substrates increased the tribo-corrosion resistance by acting as a barrier layer.

The effect of nitrogen flow rate on TiBN coatings deposited on cold work tool steel

TiBN coatings have high hardness and high adhesion. Due to these excellent properties there has been increasing interest in TiBN coatings. In this study, TiBN coatings were deposited on AISI D2 cold work tool steel and silicon wafers by closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical and adhesion properties of these coatings were analysed by X-ray diffraction, scanning electron microscopy, microhardness test, indentation test and scratch tests. TiBN coatings produced by magnetron sputtering exhibited a dense and columnar structure. These results indicate that TiB2, TiN and h-BN exist in crystalline forms at all coatings. The highest hardness was obtained at the lowest nitrogen flow rate. Very few cracks were observed at the edge of the indentation marks at the highest nitrogen flow rate. The highest critical load obtained with scratch test was identified as 102 N.

The wear behaviour of duplex treated AISI 5140 steel

Purpose – This work aims to investigate the wear behavior of manganese phosphate coating on plasma nitrided AISI 5140 steel.Design/methodology/approach – Prior to manganese phosphate coating, plasma nitriding of substrates was performed at gas mixture of 50 percent H2 and 50 percent N2, for the different treatment parameters. The structural, mechanical and tribological properties of the substrates were determined using hardness test, optical microscope, scanning electron microscopy , X‐ray diffraction and pin‐on‐disk tribotester. The wear behavior of untreated, nitrided and duplex treated substrates was evaluated under dry sliding conditions.Findings – The results indicated that the duplex treatment improved the wear behavior. It was also observed that manganese phosphating of the nitrided substrates at low temperature (450°C‐2h‐N) resulted in a decrease of the wear rate and yielded a reduction in the friction coefficient by forming a transfer film at the counter face.Originality/value – This study can be...