Başyipit, Aziz Bariş; Azakli, Zeki; Gümrük, Recep; Bican, Osman

The efficiency of thorough anodic oxidation of ASTM A356 aluminum alloy as an alternative to painting its surface is studied. Microstructure, phase composition, and microhardness of oxidized layers of various thicknesses (45, 65, 80 and 90 μm) are determined. Solid particle erosion tests are conducted in accordance with ASTM G76 and MIL STD 3033. It is established that with an increase in oxidized layer thickness aluminum alloy wear resistance is reduced and the surface roughness is reduced.

Hekimoğlu, Ali Paşa; Savaşkan, Temel; Azakli, Zeki

An attempt was made to correlate mechanical (hardness and ultimate tensile strength) and tribological properties (friction coefficient, working temperature, wear volume and average surface roughness) of Zn-40Al-2Cu-2Si alloy which was prepared by permanent mold casting. The tribological properties of the alloy were determined using a block-on-cylinder type wear test machine. The relationships between the mechanical and tribological properties of the alloy determined by linear regression analysis were observed to be expressed by linear or straight-line equations. The correlation coefficients of these relationships were found to be between 0.94 and 0.99. These linear equations indicate that the friction coefficient and the wear volume of this alloy can be calculated in terms of either its hardness or tensile strength under the given working conditions. These linear relationships also showed that as the hardness and the tensile strength of the alloy increase the friction coefficient, working temperature, and wear volume of it decrease but its average surface roughness increases. These observations were explained in terms of the microstructure and mechanical properties of the alloy, adhesion theory of friction and the Archard wear law. The equations obtained by this correlation can also be used for the selection of Zn-40Al-based alloys for bearing applications.

Savaskan, Temel; Hekimoglu, Ali Pasa; Azakli, Zeki; Calis, Merve

In order to determine the effect of working conditions on the lubricated wear behavior of Zn-40Al-2Cu-2Si alloy in the as-cast and T6 heat-treated states, its tribological properties were studied at different oil flowrates, contact pressures, and sliding speeds in comparison with SAE 660 bronze. It was observed that the friction coefficient, temperature, and wear volume of both materials decrease, but their average surface roughness increase with increasing oil flowrate. As the pressure increased, the friction coefficient and average surface roughness of the experimental materials decreased, but their temperature and wear volume increased. It was also found that the working temperature of these materials increased, but their wear volume showed a decrement and a subsequent increment with increasing sliding speed. In addition, their wear volume and average surface roughness showed opposite changes with the sliding speed. Zn-40Al-2Cu-2Si alloy in both as-cast and heat-treated conditions showed lower wear volume and friction coefficient than SAE 660 bronze. This indicates that Zn-40Al-2Cu-2Si alloy can be used to manufacture diesel engine crankshaft journal bearings.

Azakli, Zeki; Gümrük, Recep

Many critical parts such as surface parts of high-speed trains, bins and hoppers, and pipes, bends and valves in material transportation applications as well as a helicopter, mixer, and turbine blades, which can be exposed to particle wear due to the application environment, can be easily manufactured today due to the advances in 3D printing technology. For this reason, an experimental study was carried out to determine the particle erosion behavior of 316L stainless steel parts built by the laser melting method, which is one of the 3D printing technologies. The rectangular plate samples produced with various laser manufacturing parameters were subjected to particle erosion tests at different impingement angles in accordance with the ASTM G76 standard at 140 m/s impact speed. The results showed that the erosion behavior develops in a characteristic similar to the wrought sample, and laser parameters play an efficient role. For example, the porosity ratio decreases at low scanning speeds, resulting in significant improvements in erosion behavior. Also, it was found that the particle erosion behavior of the 3D printed parts could be improved in a serious amount by applying a heat treatment process. Consequently, the obtained results in this study promotes the more comprehensive works regarding the optimization of several laser manufacturing parameters such as scan speed, build direction, laser power, hatch spacing, layer thickness, scan strategy and laser exposure time to obtain the best particle erosion behavior and determination of the most suitable materials among the several others which can be used in 3D printing.