Incorporation of 3 μm SiCp into Titanium surfaces using a 2.8 kW laser beam of 186 and 373 MJ m-2 energy densities in a nitrogen environment

The formation of composite layers using a 2.8 kW laser beam of 186 and 373 MJ m−2 energy densities, on commercial purity titanium surfaces preplaced with 3 μm size, 1-4 vol.% SiCp powder in a 100% nitrogen environment, produced gold colour tracks. The tracks gave reflective surfaces after glazing at an energy density of 373 MJ m−2 and dull or a mixture of dull and shiny surfaces at 186 MJ m−2 energy density. Surface cracks were visible in tracks containing 1 and 2 vol.% SiCp, but none were observed in the 4 vol.% SiCp tracks glazed at both energy densities. In the track cross sections, vertical cracks were seen in the 373 MJ m−2 tracks but it was absent in 186 MJm−2 tracks. The SiCp particles completely dissolved in all the tracks processed in this investigation producing a complex and inhomogeneous microstructure of dendrites and needle particles. At the half way of the melt depth from the surface, the dendrites were larger and densely populated, especially after glazing at 373 MJ m−2. The hardness measurement of the MMC layer recorded a wide range of hardness values which gave loops in the hardness profiles. Hardness values ranging from 700 to 1000 Hv were observed up to a melt depth of 1 mm in many tracks and the maximum surface hardness of 2250 Hv was measured in the track containing 1 vol.% SiCp and glazed at 373 MJ m−2. The surface hardness developed 5.6-15 times the base hardness (150 Hv) depending on the dendrite population. The 3 μm size SiCp produced MMC layers 1.5-2 times greater than those previously observed with 6 μm SiCp. The large surface area for an equivalent volume fraction of the three micron carbide particles is considered to have a high laser coupling action and hence absorbed more heat energy to produce deeper melt depth compared to those produced using the 6 μm SiCp

Generation of a VUV-to-visible Raman frequency comb in hydrogen-filled kagom\'e photonic crystal fiber

We report the generation of a purely vibrational Raman comb, extending from the vacuum ultraviolet (184 nm) to the visible (478 nm), in hydrogen-filled kagom\'e-style photonic crystal fiber pumped at 266 nm. Stimulated Raman scattering and molecular modulation processes are enhanced by higher Raman gain in the ultraviolet. Owing to the pressure-tunable normal dispersion landscape of the fiber-gas system in the ultraviolet, higher-order anti-Stokes bands are generated preferentially in higher-order fiber modes. The results pave the way towards tunable fiber-based sources of deep- and vacuum ultraviolet light for applications in, e.g., spectroscopy and biomedicine.Comment: 4 pages, 5 figures, 1 tabl

Microstructure and mechanical properties of metal powder treated AISI- 430 FSS welds

Abstract: An innovative yet simple technique for the inoculation of the weld pool of commercial AISI 430 Ferritic Stainless Steel (FSS) with metal powders for grain refinement is discussed. Aluminum or titanium powder in varying amounts introduced into the weld pool via powder preplacement technique was melted under a tungsten inert gas (TIG) torch. This strategy of inoculating the welds offers dual benefits of grain refinement and constriction in the weld geometry. The addition of the metal powders constricts the HAZ by as much as 50% of the conventional weld providing a grain refinement index (GRI) of about 0.8 in titanium powder treated welds. It equally emerged that weld property is not influenced by the grain size alone but equally by the amount of delta ferrite in the microstructure

Dry/wet sliding activation wear of pure Al / R. M. Nasir...[et al.]

An experimental work to study the wear behavior of pure Aluminium (Al) block was conducted against steel counter surface in Pin-on-Disc (POD) and the aluminium ball using four ball testing (4BT) method on dry/wet sliding wear technique at room temperature. Wear test conditions of 10-50 N load with sliding speed of 20-100 rpm was used to assess the friction coefficient, wear rate and the severance of wear mechanism on the damage surface. Due to the friction from the third body abrasive and protruded Al surfaces showcased mild wear with a steady state coefficient friction ranging from 0.0019-0.0043 for dry sliding and on wet condition ranging from 0.12-0.23 in vegetable oil (with average scar area of 8.0752 mm2) and from 0.058-0.085 for mineral oil used (with average scar area of 17.1549 mm2). Stress generation of the uncoated sample allowed the abraded plastic deformation to be classified as severe wear

Low Temperature Fluidized Bed Nitriding of Austenitic Stainless Steel

In the present investigation, low temperature nitriding has been attempted on AISI 316L austenitic stainless steel by using a laboratory fluidized bed furnace. The nitriding was performed in temperature range between 400°C and 500°C. X-ray diffraction, metallography, and corrosion tests were used to characterize the resultant nitrided surface and layers. The results showed that fluidized bed process can be used to produce a precipitation-free nitrided layer characterized by the S phase or expanded austenite on austenitic stainless steel at temperatures below 500°C. But there exists a critical temperature and an incubation time for effective nitriding, below which nitriding is ineffective. The corrosion behaviour of the as-nitrided surfaces is significantly different from that previously reported for low temperature plasma nitriding. This anomaly is explained by the formation of iron oxide products and surface contamination during the fluidized proces

Maternal and Newborn-care Practices During Pregnancy, Childbirth, and the Postnatal Period: A Comparison in Three Rural Districts in Bangladesh

The aim of this study was to examine the prevalence of maternal and newborn-care practices among women reporting a birth in the previous year in three districts in different divisions of Bangladesh. In 2003, 6,785 women, who had delivered a newborn infant in the previous year, across three districts in Bangladesh, were interviewed. Overall, less than half of the women received any antenatal care, and 11% received a minimum of four check-ups. Only 18% took iron tablets for at least four months during pregnancy. Over 90% of the 6,785 deliveries took place at home, and only 11% were attended either by a doctor or by a nurse. The mothers reported three key hygienic practices in 54% of deliveries: at\uadtendants washing their hands with soap and boiling cord-tie and blade for cutting the cord. Forty-four percent of the 6,785 infants were bathed immediately after delivery, and 42% were given colostrum as their first food. The results suggest that maternal and newborn-care remains a cause of concern in rural Bangladesh. Short-term policies to promote healthy behaviour in the home are needed, in addition to the long-term goal of skilled birth attendance

Wear behaviour at 600°C of surface engineered low-alloy steel containing TiC particles

The work aimed to develop surfaces that could resist wear at high temperatures, thus achieving a prolonged component life. Surface modification of a low-alloy steel by incorporating TiC particles has been undertaken by melting the surface using a tungsten inert gas torch. The dry sliding wear behaviour at 600°C of the original and modified surfaces was compared. Microscopic examination of both surfaces showed glazed layers across the wear tracks, with differing amounts of oxide and homogeneity. Extensive wear occurred on the steel surface, which showed deformation of the wear scar tracks and a steadily increased friction coefficient. The TiC addition reduced the wear loss, coinciding with a glazed layer 33% thinner than that on the low-alloy steel sample