In the present study, the effect of Sn on the dry sliding wear behavior of spray formed and hot pressed Al17Si alloy as a function of applied load and sliding speed has been investigated and compared with that of as-cast alloy. The microstructure of spray formed Al-17Si alloy consists of fine and uniformly distributed Si particles and that of Al-17Si-10Sn alloy consists of fine and uniform dispersion of Si particles and ultra-fine Sn particles in a-Al matrix. Coarse and segregated microstructures were observed in as-cast alloys. The wear resistance of spray formed alloys is higher than that of as-cast alloys. The wear resistance of as-cast Al-17Si-10Sn alloy is higher than that of as-cast Al-17Si alloy. The high wear resistance of spray formed Al-17Si-10Sn alloy is discussed in the light of its microstructural features and the nature of worn-out surfaces.
Abstract:The effect of process parameters on the characteristics of Al-17Si alloy powder produced by gas atomization using a free fall nozzle of different apex anglesof different apex angles was investigated. The axial gas velocity of gas jet away from the nozzle exit is measured for different operating pressures. The alloy was melted to a superheat temperature of 100,150 and 200°C and atomized by varying the gas flow rate and melt flow rate. The alloy powder size analysis were carried out by ASTM standard sieve with vibratory shaker and characterization of powder particles was accomplished by the parameters such as mass media, average size of powder particles; standard deviation and morphology of powder were studied by scanning electron microscopy. It is observed that decrease of apex angle results in axial velocity decreases in entire applied gas pressures range. Increase in apex angle results in decrease of gas jet length to metal stream collision, the median particle diameter of the powder increases resulting in decrease in particle irregularity. The median particle diameter of the powder has been shown to decrease almost linearly with increase in gas to melt flow (G/M) ratio. The sauter mean diameter variation, however, decreases slowly with increase in G/M ratio. Median particle diameter is significantly reduced with increase in the melt superheat.
The microstructure characteristics and wear behavior of a spray-deposited (SD) and the hot compressed Al-28Si alloys were investigated and the results were compared with corresponding SD and as-cast alloys. The microstructure, hardness and wear properties of the spray-deposited alloy was studied using X-ray diffraction, optical microscopy, scanning electron microscopy (SEM), microhardness measurement and wear tests. The microstructures of the SD alloy were composed of refined and uniformly distributed primary silicon (Si) and the formation a fine eutectic phase at the inter particle boundaries of an equiaxed grain morphology of the aluminum (Al) matrix. The decrease in the porosity level and further refinement of primary Si and eutectic Si phases in the hot pressed alloy. The wear tests indicate that the hot pressed spray formed alloy showed good wear resistance compared to both the SD and as-cast alloys. The improvement in the wear behavior is discussed in the light of microstructure evolution by the spray-deposition process. The worn surfaces were characterized by SEM-energy dispersive X-ray spectroscopy (EDS).
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