Sharif Digital Repository

In this paper, sliding friction and wear behaviors of gray cast iron A35 and white cast iron manufactured by quenching from the same cast iron in water were studied and compared by employing pin-on-disk wear tests. Microstructure of the worn surfaces before and after the wear tests were investigated by optical microscope observations. These images show that flakes separated from the surface in gray cast iron due to delamination process, while in white cast iron, the separation of materials from its surface is in the form of powder. In addition, the gray cast iron had higher graphite volume fraction with Type-A graphite flake morphology. The results show that white cast iron has less rate of... 

Tungsten Inert Gas (TIG) process and titanium cored wires filled with micro size TiC particles were employed to produce surface composite coatings on commercial pure Ti substrate for wear resistance improvement. Wire drawing process was utilized to produce several cored wires from titanium strips and titanium carbide powders. Subsequently, these cored wires were melted and coated on commercial pure Ti using TIG process. This procedure was repeated at different current intensities and welding travel speeds. Composite coating tracks were found to be affected by TIG heat input. The microstructural studies using optical and scanning electron microscopy supported by X-ray diffraction showed that... 

In this study, high-vanadium austenitic manganese steel (HV-AMS) alloys and the standard Hadfield steel were investigated. The microstructure of these high-vanadium alloyed Hadfield steels was studied thoroughly using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and was compared to the Hadfield steel. The hardness and unnotched Charpy impact strength of HV-AMS alloys and Hadfield steel were examined at ambient temperature in the as-cast and heat-treated conditions. A pin-on-disk wear test at linear speed of 10. m/min and a 55. N normal load was employed to evaluate the wear behavior of both steel samples. Microstructural results showed that varying... 

Aluminum matrix in situ nanocomposite was produced by one to six passes friction stir processing (FSP) with pre-placed Fe3O4 nanoparticles (15-20 nm). Microstructure studies showed that solid-state reactions between the aluminum matrix and Fe3O4 particles during the process led to in situ formation of Al3Fe and Al5Fe2 in the stir zone. Initial Fe3O4 as well as Al-Fe intermetallic compounds (IMCs) particles were homogeneously dispersed in a fine grain matrix after six passes of FSP. Hardness and ultimate tensile strength of the composites were increased 64 and 27%, respectively, compared to the base metal. The reasons were studied in the light of reinforcing particles distribution, formation... 

In the present study, the wear behaviour of Cu-Al2O3 composites and Cu-Al alloys has been investigated. The experiment involved casting of Cu-Al alloys with 0•37, 1, 2 and 3 wt-% of aluminium under inert gas atmosphere. The composites were produced by internal oxidation of alloys at 950°C for 10 h in presence of Fe2O3 and Al 2O3 powders mixture. The microstructures of composites were studied using SEM and atomic force microscopy. To identify wear behaviour of specimens, dry sliding pin-on-disk wear tests were conducted according to ASTM G99-95a standard. The normal loads of 20, 30, and 40 N were applied on specimens during wear tests. The sliding speed and distances were selected as 0•5 m... 

Production of Al1050/TiO 2 -graphite hybrid nanocomposite via friction stir processing (FSP) was studied. The effect of graphite-to-TiO 2 volume fraction ratio (Gr/TiO 2 ), at a constant rotational speed (ω) and three levels of tool traverse speed (ν), on the microstructural evolution and mechanical properties of the nanocomposites was investigated. While TiO 2 is supposed to enhance the strength and hardness, graphite is believed to improve the tribological behavior. Furthermore, formation of intermetallic compounds (IMCs) through the solid-state reactions between the reinforcements and aluminum matrix may also promote the mechanical properties. To assess these assumptions, longitudinal and... 

In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also,... 

In this present study, Tungsten Inert Gas (TIG) welding and powder filled cored wires with nitrogen shielding gas were utilized to produce TiC and TiN surface composite coatings on the titanium (Ti) sheet substrate. The TIG procedure was done at same welding parameters for all of prepared samples. Phase analysis and microstructures were done by X-ray Diffraction (XRD), Energy-Dispersive X-ray Spectroscopy (EDS), Optical Microscopy (OM) and Scanning Electron Microscopy (SEM). The obtained results from XRD and EDS demonstrated that the presence of crystalline phases of TiC, TiN and Ti. SEM and OM exhibited formation of the spherical and dendritic TiC particles in a martensitic matrix and also,... 

The effects of severe shot-peening process and formation of a nanostructured surface layer on mechanical properties of A356.0 alloy were investigated in this paper. X-ray diffraction analyses revealed that the average size of near-surface grains in severe shot-peened specimens is 75.8 nm. Three types of disk-shaped specimens, non-treated, conventionally shot-peened, and severely shot-peened were subjected to pin-on-disk wear test in the dry condition, in different loading and sliding speeds. Shot-peening process increases both hardness and roughness of the surface, and these two factors have, respectively, positive and negative effects on wear resistance. However, because of high-density... 

The tribological behaviors of an AISI 4340 ferritic-bainitic dual-phase steel with different bainite (VB) content were investigated. The effects of VB on wear resistance and the corresponding wear mechanisms were investigated using a pin-on-disk wear testing machine, at normal loads of 10 and 50 N, at a constant sliding velocity. The tensile and hardness tests showed that the yield strength, ultimate tensile strength, and hardness increased with increasing the VB. The wear test results at the 10 N normal load showed a direct correlation between the tensile and tribological behavior of the samples. Nevertheless, at the normal load of 50 N, unexpected behavior was observed due to the carbon... 

The internal Oxidation introduces a practical method for producing copper matrix composites reinforced by alumina particles. The mechanical and physical properties of alumina reinforced copper composites and alloy specimens were investigated. This experiment involves casting of Cu-Al alloys with 0.37, 1, 2 and 3 weight percent of aluminium in non-oxidizing atmosphere with pure oxygen free copper. The composite specimens produced after internal oxidation process at 950°C for 10 hours in sealed alumina crucible. The microstructures of composite specimens were studied after internal oxidation using SEM and AFM. The hardness and electrical resistivity tests were measured. The wear properties of...