Ilyas Uygur

Machinability of AISI 316 Austenitic Stainless Steel With Cryogenically Treated M35 High-Speed Steel Twist Drills

In this paper, machinability of AISI 316 austenitic stainless steel was investigated usingcryogenically treated and untreated high-speed steel (HSS) twist drills. Machinability ofAISI 316 austenitic stainless steel was evaluated in terms of thrust force, tool life, surfaceroughness, and hole quality of the drilled holes. Experimental results showed from 14%to 218% improvements for treated tool lives. Thrust force, surface roughness, and holequality are better with treated drills when compared with untreated drills. Theseimprovements were mainly attributed to formation of fine and homogeneous carbide par-ticles and transformation of retained austenite to martensite. Microhardness and micro-structure observations verified these formations. [DOI: 10.1115/1.4007620]Keywords: microstructure, hardness, stainless steel, cryogenic treatment, machinability

Effect of Porosity Content on the Weldability of Powder Metal Parts Produced by Friction Stir Welding

Friction stir welding technique (FSW) has many advantages in terms of tool design, rotational speed and traveling speed, and can be adjusted in a precise manner. It enables heat input into the system to be controlled. In this study, Aluminum powders were compacted at 350,400 and 450 MPa pressure and sintered at 450 oC temperature for 30 minutes in Ar atmosphere. Sintered powder metal parts were joined to each other by FSW at the speed of 1800 rpm and traveling welding speed 200 mm/min under a constant friction force. The results show that the amount of porosity affects the weldability of powder metallurgy (P/M) parts. Furthermore, the porosity and microstructural evolution of the Aluminum also affected the hardness values of the tested materials.

The Effects of Cryogenic Treatment on the Corrosion of AISI D3 Steel

It is well known that cryogenic treatment is used to improve the mechanical properties of a material. Consequently, the use of cryogenic treatment has grown beyond its successful application on tool steels. In this research, the effects of cryogenic treatment on the corrosion of AISI D3 steel in 3.5% NaCl solution were examined by electrochemical impedance spectroscopy (EIS). The surface structure of the AISI D3 steel was examined by scanning electron microscopy (SEM) after the EIS investigations. Results clearly indicated that the pre-treatment of the steel was responsible for a significant effect on corrosion. The heat treatment process prior to the cryogenic treatment and the tempering process after were shown to decrease corrosion resistance.

The microstructure and mechanical properties of joints of technical-grade aluminium gas welded with oxygen–hydrogen flame

The goal of this study was to investigate the weldability of aluminum by using the oxy-hydrogen welding technique. Specimen dimensions were 1.5 mm in thickness and 80 mm in length. Microstructural investigations on the cross-sectional area of the weld zone were also carried out in order to compare weld metal and HAZ depending on the welding gases. Tensile strength and microhardness tests were carried out and the results were compared. Test results have shown that the yield strength of the samples welded with oxy-acetylene is higher than that of the samples welded with oxy-hydrogen.

Effects of Temperature on the Weldability of Powder Metal Parts Joined by Diffusion Welding

Diffusion welding is an advanced bonding process in which similar or dissimilar materials can be bonded in solid state. In this study, aluminium composite (5% and 15% WC) powders were compacted at 450 MPa pressure and sintered at 550 oC for 45 minutes in argon atmosphere.and joined each other by diffusion bonding. The bonding temperatures (585 oC, 600 oC, 615 oC) and dwell time (185 min) were chosen for the welding process at constant 20 MPa. It has been observed that these variations on the welding parameter strongly affected the microstructure and the weldability of the materials.

Microstructure and Performance in Diffusion Welded Joints of Al +5-10-15% WCp Composites

Joining parts by diffusion welding is one of the recent manufacturing techniques, since it allows manufacturing of similar or dissimilar parts, and complex components with high precision. It is difficult to weld Aluminium and its composites by conventional fusion welding techniques. Thus, In this study, diffusion welding technique was applied to weld Al+5-10-15% WCp composites in argon gas. An experimental set up has been designed and series of experiments have been performed, Metallographical examinations have been carried out to determine the welding quality. It was concluded that changes in volume fraction of the reinforcement particles strongly affect the weldability of the materials and their microstructures.

Advanced friction-wear behavior of organic brake pads using a newly developed system

Abstract The objective of this study was to investigate the influence of an advanced performance system on the tribological behavior of brake pad material using a specially designed brake pad tester system following standard SAE J-661. The tribological behavior and friction and wear characteristics of the organic brake pad samples were evaluated. During braking tests, the samples, in contact with a cast iron disk, were studied at different disc speeds, temperatures, and braking cycles under a constant pressure. In order to understand the friction and wear behavior, the unworn surfaces, worn surfaces, and wear debris were characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). Furthermore, the surface characteristics and differences in the wear modes of the brake pad samples were examined. Wear debris was permitted to deform the brake pad surfaces, leading to friction layers and enabling the estimation of the friction behavior of the brake pads. The results showed that the best friction–wear behavior was obtained with lower braking cycles at low speeds and temperature. Thus, the newly developed brake pad tester system proved very effective in evaluating the performance of the brake pad samples.

Development of A New Type Brake Pad Frıctıon Tester

An improvement in automotive industry; high coefficient of friction and wear resistance-non asbestos friction pads can be produced. Various types of test apparatus are constructed for wear, friction and noise level detection. In this study, natural dust reinforced brake pads were tested and characterized by SAEJ-661 standards. For this purpose computer aided new type of brake pad friction tester produced. This test machine consists of hydraulic control, mechanical design, and automation systems. The main difference of this new type of tester compared to other is that brake pads can be tested in real dimension and test conditions with high precision. Also noise levels can be measured by the test machine. At the end of the study, real brake pad friction responses can be determined with fast and high precision by newly developed friction pad tester. The friction coefficient is increased rapidly at the beginning with the disc speed increased and the started to decrease and then continued constantly. From this, it is concluded that the whole brake pad pattern is related to surface contact and two interface resistances.

Evaluation of The Physical Properties of Hazelnut Shell Dust-Added Brake Pad Samples Treated With Cryogenic Process

After understanding that asbestos fibers are harmful to human health; researchers have investigated for alternative and eco-friendly materials. Agricultural products can be an example of these alternative and environmentally friendly materials because they are easily supplied . Thus, in this study, asbestos-free automotive brake pads produced from %7 hazelnut dusts with other seventeen additives. Hazelnut shell is preferred because it is widespread in our country. Cryogenic process applied at -80°C to the brake pads. Before and after cryogenic treatment, the produced brake pads properties such as water absorption, hardness test, porosity and microstructural examinations were investigated. The hardness values of brake pads increases after cryogenic and cyclic-cryogenic process. The highest values obtained for the B-CYC sample.

Characterization of Water and Oil Absorption Properties of Organic Additive Brake Pad Samples

Alınma: 19.01.2018 Kabul: 09.03.2018 Son yıllarda otomotiv teknolojisinin gelişmesiyle birlikte, fren balatası için alternatif kompozisyon arayışı da artmıştır. Kompozisyonunda birçok tozu barındıran fren balatalarının, performansının yanında, alternatif tozlardan üretilmesi de beklenmektedir. Alternatif tozlarda, çevre dostu olması ve maliyetinin düşük olması istenen en önemli faktörlerdendir. Bu çalışmada, ülkemizde yüksek rezerve sahip boraks ve wollastonite kullanılmıştır. Alternatif tozlarla üretilen fren balatası numunelerinin su ve yağ emme davranışları test edilmiştir. Elde edilen sonuçlar referans olarak kullanılan ticari fren balataları ile kıyaslanmıştır. Suda bekletilen numunelerin sertlik değerleri, yağda bekletilen numunelere göre daha fazla düşmüştür. Katkı maddesi olarak wollastonite kullanılan numunelerde daha az sertlik değişimi gözlenmiştir. Boraks katkılı fren balatalarının yoğunluk değerleri referans fren balatasına daha yakın değerlerdedir. Wollastonite katkılı fren balatalarında gözlemlenen ağırlık değişimi ise ticari fren balatası numunesine yakın değerlerde elde edilmiştir.