H. Cuvalci

Microstructure and Abrasive Wear Behavior of CuSn10–Graphite Composites Produced by Powder Metallurgy

In this study, CuSn10 metal-matrix composites (MMCs) reinforced with 0, 1, 3, and 5 vol.% graphite particulates were fabricated by powder metallurgy. The microstructure, relative density, hardness, and abrasive wear behavior of the composites were investigated. The abrasive wear tests were conducted on unreinforced matrix and CuSn10–graphite composites using a pin-on-disk-type machine. The effects of sliding distance, applied load, graphite particle content, and abrasive grit sizes on the abrasive wear properties of the composites have been evaluated. The microstructure evolution of composites and the main wear mechanisms were identified using a scanning electron microscope and an energy-dispersive X-ray spectrometer (EDS). The density and hardness of the sintered CuSn10–graphite composites decreased with increasing graphite content. The abrasive wear resistance increased with increasing graphite content, but the abrasive wear resistance decreased with increasing sliding distance, applied load, and abrasive grit size. Moreover, the wear resistance of the composite was found to be considerably higher than that of the CuSn10 matrix alloy and increased with increasing graphite particle content.

A NEW TEST APPARATUS AND METHOD FOR FRICTION FORCE MEASUREMENT IN JOURNAL BEARINGS UNDER DYNAMIC LOADING: PART II

Automotive engineers have recently made intensive investigations to increase the performance and efficiency of internal combustion engines. One of the main ways to increase engine efficiency is to decrease frictional losses at the moving part of the engine. An approximate energy loss in an automobile is as much as 510 W or 0.7 HP.1 An engine has a wide variety of friction sources such as crankshaft and connecting rod bearings, cam-tappet mechanism, piston-cylinder system, and so on. It is clear that journal bearings (crankshaft and connecting rod) are one of the main power losses of an engine.2 Researchers have done many studies to improve performance and properties

Development and characterization of bronze-Cr-Ni composites produced by powder metallurgy

Abstract In this study, the bronze-Cr-Ni composites were prepared by means of the powder metallurgical method. The influence of the composition and compact pressure on microstructure, density, hardness and electrical conductivity was examined. Scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX) were used to analyze the microstructure of the contact materials. The results showed that density of the bronze-Cr-Ni composites decreased with increasing Ni content. Increasing compact pressure led to lower porosity and consequently improved the density of bronze-Cr-Ni composites. The relative green density increased from 78% to 95% with the increase in the compact pressure from 200 MPa to 800 MPa. The hardness values showed a decrease from 95.1 BHN to 71.6 BHN by the addition of Ni from 1 wt% to 5 wt% at 800 MPa. It was found that addition of Ni at 1 wt% was required to achieve increased hardness and sufficient conductivity for bronze-Cr-Ni composites. The electrical conductivities of contact materials containing 3 wt% Ni and 5 wt% Ni was lower than that of 1 wt% Ni.

Tribological behavior of ZA27/Al2O3/graphite hybrid nanocomposites

ABSTRACT ZA27 alloy composites reinforced with alumina and graphite nanoparticles are a unique class of advanced engineered materials that have been developed to use in tribological applications. In this study, dry sliding wear behavior of ZA27 alloy matrix hybrid nanocomposites has been investigated. Mechanical alloying and hot pressing methods have been used for the fabrication of these composite materials. Sliding wear tests were conducted using a block-on-disc type sliding wear testing apparatus under unlubricated conditions. Scanning electron microscopy analyses have been carried out to examine the wear surfaces. The results showed that the increase of alumina nanoparticle content can positively influence improvement of the tribological behavior of the hybrid nanocomposites.

Effect of nano-sized B4C addition on the mechanical properties of ZA27 composites

In order to understand the influence of nano-sized B4C additive on ZA27 alloy, mechanical and physical properties of ZA27-B4C nanocomposites were investigated in terms of B4C content. While physical properties were determined in terms of microstructural studies, density and porosity tests, mechanical properties were determined in terms of ultimate tensile strength (UTS) and hardness experiments. Morphological and microstructural studies were carried out with scanning electron microscopy (SEM). The experimental results indicate that nano-sized B4C can be used to enhance the mechanical properties of ZA27 alloy effectively. The highest mechanical performance can be obtained at ZA27-0.5% B4C (in weight) nanocomposite with values of tensile strength (247 MPa) and hardness (141,18 BH) and low partial porosity (0.5%). After a pick point, increasing B4C ratio may cause the formation of agglomeration in grain boundaries, that’s why density, tensile strength, and hardness values are declined.