Fehim Findik

Investigation of explosive welding parameters and their effects on microhardness and shear strength

The aim of this study was to investigate the strength of explosive welded metals with the same chemical compositions. Different welding interfaces (straight, wavy and continuous solidified-melted) were used with changing explosive welding parameters [stand-off distance (s), explosive loading (R) and anvils]. Joined metals were investigated under heat-treated and untreated conditions. Results on the microstructure, microhardness, tensile shear strength and bending tests are reported. According to the experimental results, the effect of the anvil on the explosive welding process was only the joining or not-joining performance. It was shown that the bonding interface changed from a straight to a wavy structure when the explosive loading and stand-off distance were increased. For wavy interfaces, when the explosive loading was increased the wavy length and amplitude increased. Results of tensile shear and bending tests showed that heat-treated specimens have more strength than untreated samples. According to tensile shear test results, straight and wavy interfaces had similar strength. In addition, in bending tests of untreated specimens it was shown that the bending zone had some cracks.

Microstructure, hardness and electrical properties of silver-based refractory contact materials

Abstract The electrical conductivity, hardness and microstructure of Ag–W and Ag–WC refractory contact materials have been investigated. Ag–W composites containing 30, 35, 45 and 85 wt.% of silver and Ag-40 wt.% WC composite produced by powder metallurgy were used for this investigation. The effect of graphite addition on hardness and electrical conductivity of Ag–WC composite was also evaluated. The present results show that the electrical conductivity of Ag–W composite increased with increasing Ag content, but decreased its hardness. The addition of WC to Ag increased its hardness, but decreased its electrical conductivity as compared with the addition of W to Ag. The addition of 3 wt.% C to Ag-37 wt.% WC composite decreased both its hardness and electrical conductivity.

The influence of some factors on steel/steel bonding quality on there characteristics of explosive welding joints

Explosive welding is a solid state process in which controlled explosive detonations force two or more metals together at high pressures. The resultant arrangement is joined with a high quality metallurgical bond. The aim of this study was to investigate of strength of explosive welding metals which had same chemical compositions. In this study, it was taken different welding interfaces (straight, wavy and continuous solidified-melted) with changing explosive welding parameters (stand-off distance (s), explosive loading (R) and anvils). Joined metals were investigated in heat treatment and non heat treatment conditions. Microstructures, microhardness, tensile shear strength and bending test results were reported. Effect of anvil on explosive welding process was evaluated in joining/no joining performance. It was shown that bonding interface changed from straight to wavy structure when explosive loading and stand-off distance were increased. On wavy interface, when explosive loading was increased wavy length and amplitude increased. Results of tensile shear and bending tests showed that heat treated specimens have more strength than which of unheat-treated ones. According to tensile shear test results, straight and wavy interfaces had similar strength. Also, bending zone has shown some cracks after the bending test of unheated specimens.

Friction and wear behaviour of implanted AISI 316L SS and comparison with a substrate

Ion implantation creates alterations in surface composition or morphology of solids which yield to a modification of physical and especially mechanical properties; such as hardness and modulus of elasticity. The aim of this study is to focus on the friction and wear behaviour of N2 and Zr implanted and TiN coated 316L stainless steel and compare with a substrate. Particularly, stainless steels were of interest, because they often display a poor tribological behaviour, which can be improved when they are hardened by incorporating N2, TiN and Zr and forming a hardened surface zone. The present implantations were shown to improve the friction coefficient as well as the wear resistance of the stainless steel surface.

Ballistic impact performance of composite structures

One of the materials commonly used in the aerospace and automotive industries is polymer-based composites. It also has potential for even greater usage. In this paper the ballistic impact performance of some polymer-based composites is experimentally considered. This entailed the manufacture of a number of thermosetting resin composite specimens using the hand lay-up process. Thereafter ballistic testing was carried out using a variety of commonly available firearms with the resulting properties experimentally obtained using mechanical and ultrasonic methods. The results were compared relatively with previous studies. Finally the potential benefits for using such materials on an armoured saloon car is highlighted.

Ballistic impact efficiency of polymer composites

The use of polymer-based composite materials in the aircraft and automotive industries has been rapidly increasing. In this paper the impact efficiency of some polymer-based composites is experimentally studied. This involved the manufacture of a quantity of thermosetting resin composite specimens using the hand lay-up process. Subsequently ballistic testing was performed using a selection of commonly available firearms with the resulting characteristics experimentally obtained using mechanical and C-scan methods. The results were compared relatively and with previous studies. Eventually the promising advantages for using such materials on an armoured car are emphasized.

Comparative study of wear mechanism of surface treated AISI 316L stainless steel

Coating is a technique employed for the surface of materials to have thermal insulation, hot corrosion and oxidation resistance. Ion implantation forms modifications in surface composition or morphology of solids which yield to a change of physical and especially mechanical properties such as hardness and modulus of elasticity. The objective of this investigation is to concentrate on the friction and wear behaviour of TiN, N2 and Zr implanted and TiN and Tinalox PVD coated 316L stainless steel and compare with a substrate. Mainly stainless steels were of attraction, because they frequently demonstrate a poor tribological behaviour, which can be enhanced when they are hardened by incorporating N2, TiN Tinalox and Zr and forming a hardened surface zone.

Microstructure and mechanical properties of injection moulded Nimonic-90 superalloy parts

Abstract This study aims to determine optimum sintering and heat treatment parameters of powder injection moulded Nimonic-90 powder parts. Determination of optimum heat treatment conditions for sintered parts aimed to achieve maximum densities, and the microstructure and mechanical properties of the produced parts were characterised in sintered and heat treated conditions. Injection moulding feedstock was prepared by mixing Nimonic-90 powder with a multicomponent binder system. After moulding, the samples were subjected to a debinding process that consists of solvent and thermal steps. To determine the sintering temperatures, the debinded samples were subjected to differential scanning calorimetry analysis, and then they were sintered at various temperatures under high level vacuum. After sintering, density measurements and optical microscope examinations were performed. The highest density values were determined for the samples that were sintered at 1330°C for 3 h. Different aging treatments were performed on the samples that achieved the highest sintered density, and the microstructures and mechanical properties were then characterised. It was determined that heat treatments had a beneficial effect on the mechanical properties of the material. Though the mechanical properties of the injection moulded materials produced were lower than the wrought Nimonic-90 materials, they have superior mechanical properties compared with cast Nimonic-90 alloys.

Friction and wear behaviours of some industrial polyamides against different polymer counterparts under dry conditions

Purpose – The present study aims to find out the best polymer/polymer pair in electrical insulating applications. Moreover, the effects of different polymer counterpart and applied load on the friction and wear behaviour of PA 46 + 30%GFR and unfilled PA 66 thermoplastic polymers are to be studied.Design/methodology/approach – Friction and wear tests vs PA 46 + 30%GFR and PPS + 30%GFR polymer composites were carried out on a pin‐on‐disc arrangement and at a dry sliding conditions. Tribological tests were performed at room temperature under 20, 40 and 60 N loads and at 0.5 m/s sliding speed.Findings – The results showed that, the coefficient of friction decreases with the increasing of load (up to 40 N) for PA 46 + 30%GFR composite and polyamide (PA) 66 polymer used in this study. However, above 40 N applied load the coefficient of friction increases. The specific wear rate for PA 46 + 30%GFR and PA 66 against PPS + 30%GFR polymer composite counterpart are about in the order of 10−13 m2/N while the specifi...

Influence of Process Parameters on the Mechanical and Foaming Properties of PP Polymer and PP/TALC/EPDM Composites

In this study, PP and Talc/EPDM/PP composite materials are used. Foaming process is achieved by a conventional injection molding method. The influence of injection pressure and melting temperature on the average cell dimension, cell number, skin layer thickness, foam density and mechanical properties of investegated foam materials were evaluated. It is observed that cell density is increased by the increment of injection pressure. However, the values of skin layer thickness, density, cell diameter and charpy impact strength are decreased. In addition, the values of skin layer thickness, cell density, density and impact strength are increased with the increment of melting temperature.