S. Ozkaya

New Coating Technique for Al–B4C Composite Coatings by Mechanical Milling and Composite Coating

Mechanical milling (MM) process as a novel technique for producing Al–B4C composite coatings on the surface of low carbon steel was investigated. The coating thickness, morphology, and cross-section microstructure of the composite coatings were analyzed with scanning electron microscopy (SEM). Also, Vickers microhardness and surface roughness of the coating layer were measured. It was found that a dense Al–B4C composite coating could deposit on the surface, particularly, if longer milling periods. The microstructure of Al–B4C composite coatings revealed that the distribution of B4C particles in the Al matrix was homogenous. Increasing milling time from 6 to 30 h resulted in increase of the microhardness values from 220 to 280 HV for the pre-interface layer (5 μm).

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.

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.

Determining the effect of flake matrix size and Al2O3 content on microstructure and mechanical properties of Al2O3 nanoparticle reinforced Al matrix composites

ABSTRACT In this study, Al2024 matrix composites reinforced with Al2O3 nanoparticle contents ranging from 1 to 5 wt% were produced via a new method called as flake powder metallurgy (FPM). The effect of flake size and Al2O3 nanoparticle content on the reinforcement distribution, microstructure, physical, and mechanical properties of the composites were studied. SEM analysis was performed to investigate the microstructure of metal matrix and the distribution of nanoparticles. The hot-pressed density increased with decreasing the matrix size. The hardness of the Al2024–Al2O3 nanocomposites fabricated by using fine matrix powders increased as compared to the Al2024–Al2O3 nanocomposites produced by using coarse matrix powders. It has been found that the FPM method proposed in this study revealed to be an effective method for the production of nanoparticle reinforced metal matrix composites.

Artificial neural network-based prediction technique for coating thickness in Fe-Al coatings fabricated by mechanical milling

ABSTRACT The objective of this study was to evaluate the effect of milling time, milling speed and particle size of initial powders on the coating thickness of Fe-Al intermetallic coating by using artificial neural network (ANN). Coating morphology and cross-section microstructures were evaluated using a scanning electron microscope (SEM). It was found that an increase in the milling time provided an increase in the coating-layer thickness due to the cold welding process between particles and the steel substrate. The microstructure of the coating surface was refined by ball impacts in the milling process. As a result of this study, the ANN was found to be successful for predicting the coating thickness of Fe-Al intermetallic coatings. The correlation between the predicted values and the experimental data of the feed-forward back-propagation ANN was quite adequate. The mean absolute percentage error (MAPE) for the predicted values didn’t exceed 7.46%. The ANN model can be used for predicting the coating thickness of Fe-Al intermetallic coating produced for different milling time, milling speed and particle size.