By means of slow solvent evaporation method, single crystals of Strontium chloride-doped Tetrakis Thiourea Barium Chloride (STTBC) were grown. Single crystal X-ray diffraction study has been utilized to get the values of cell parameters and to establish the monoclinic nature of the STTBC crystal. The powder XRD diffractogram defined the crystalline nature of the STTBC sample. The UV-Vis spectral study on STTBC has been employed to figure out its transmittance and cut-off wavelength. The values of significant optical constants such as reflectance, band gap energy and refractive index have also been calculated using UV-Vis spectral study. Vickers micro hardness analysis has been carried out to ascertain the mechanical strength of the synthesized crystal. The mechanical studies have inferred that the STTBC crystal exhibited reverse indentation size effect. The SHG efficiency of the STTBC sample has been observed to be 1.06 times higher than that of the parent crystal TTBC.
AISI H13 material finds wide use as screw shafts and screw elements in Twin Screw Extruders for Polymer Compounding applications owing to its high strength, excellent thermal shock resistance, high wear resistance and good fatigue strength. However, two AISI H13 shafts used in the Twin Screw Extruder supplied for fluoropolymer application experienced breakage after two years of service. Visual examination of broken shafts revealed deposits of processing material, rust marks and grooves at multiple locations on the shaft spline at the element to element butting zone. The location of breakage of the shaft was noted at Barrel No.5, which happens to be the vent zone of the extruder. The fracture surface was observed to be almost perpendicular to the rotating axis of the shaft. Macro-examination of the shafts showed abnormal wear at the groove areas and significant reduction in the diameter of the screw shafts with complete absence of spline in the zone adjacent to fracture. Hardness survey revealed values of 25-27 HRC that was 18-20 HRC lower than the hardness in supply condition. Microstructural examination on the failed shafts showed fine spheroidized carbides with ferrite in tempered martensitic matrix. SEM Analysis on samples from fracture surface revealed presence of multiple micro-voids and indicated coalescence of these voids. Based on the investigation & analyses it was inferred that the predominant mode of failure of the shafts had been “Corrosion Assisted Ductile Rupture” in elevated temperature operating conditions. Finally, recommendation to prevent occurrence of such failures has been proposed.
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