S.K. Nath

Study of Electrical and Optical Properties of Zr-Doped ZnO Thin Films Prepared by DC Reactive Magnetron Sputtering

This paper establishes DC reactive magnetron sputtering as synthesis process for Zr doped ZnO thin film. Zr can be doped in ZnO using various techniques. Some research groups have doped ZnO with Zr by radio frequency magnetron sputtering using target made of ZnO and ZrO2 powder. Radio frequency has low rate of deposition because deposition takes place only in one of two half cycles. Uniform mixing of small amount of ZrO2 powder in ZnO is expensive process as well as time consuming. To overcome the constraints, Zn and Zr metal target was used and film was made by DC reactive magnetron sputtering. Various parameters of the process was established by varying variables, such as sputtering power of the Zn and Zr, oxygen partial pressure in the chamber. Optimum flow rate of Argon is 16 sccm and Oxygen is 4 sccm. Sputtering power of 150 watt for Zn and 10 watt for the Zr gives good result. Films obtained are polycrystalline with a hexagonal structure and have preferred orientation along the c axis. Resistivity of the film is as low as 0.07 Ω-cm. Average transparency of film is above 85% in visible range.

Slurry Erosion Response of Heat Treated 13Cr-4Ni Martensitic Stainless Steel

In the present work, effect of various heat treatments on slurry erosion behavior of 13Cr-4Ni martensitic stainless steel (MSS) at different impingement angles has been studied. The as-received cast bars of MSS were given various heat treatments. These heat treatments involved the austenitization of cast steel at temperatures of 950° C, 1000° C and 1050° C for different soaking durations of 2, 4 and 6 h at each temperature. This was followed by oil quenching then tempering for 1 h at a 600° C air cooled. Heat treated MSS samples were characterized for microstructure and mechanical properties viz. hardness, ductility (% elongation), tensile strength (UTS), and toughness. For wear characterization, slurry erosion tests were conducted at different impingement angles for as-received cast and heat treated samples. The heat treated MSS shows approximately 34% lesser weight loss as compared to as-received cast MSS. Increase in toughness of heat treated samples is found to be responsible for the improved slurry erosion resistance. Impingement angle close to 0° showed least wear loss.

Cavitation and Slurry Erosion of Aluminum in the Slurry Pot Tester

In harnessing clean and renewable energy sources water turbines represent a significant portion of the power generation worldwide. Because of erosion, repair and maintenance of hydraulic turbines is a difficult problem. Material removal in hydraulic turbine components may occur either by particle erosion or cavitation erosion or by their combined action. Many ASTM standard and non standard test rigs are aimed at specific tests, like solid particle erosion, cavitation erosion. To simulate the real conditions in a laboratory setup, a novel method is employed to combine the effect of cavitation erosion and slurry erosion in the slurry pot tester. Triangular prismatic cavitation inducers are used in the conventional slurry pot tester. The aluminum test specimens are investigated in the slurry pot tester. A wide variation in material loss was noted under different exposure conditions. The maximum material loss is ascribed to combined effects of solid particle erosion and cavitation erosion.

Effect of Deposition Parameters & Molybdenum Percentage on Nickel-Molybdenum Alloy Coatings

The use of Potassium-phosphate baths for the alloy deposition of Nickel–Molybdenum is recently proved equally good as Sodium-citrate baths. The coatings so obtained from Potassium-phosphate baths were examined for atomic weight percentage of Molybdenum. The variation in weight percentage of Molybdenum was obtained by varying different plating parameters like - molar ratio, current density range, and potential range. The observed co-deposited Molybdenum Atomic percentage variation in alloy was investigated for grain size, porosity in structure and surface roughness. The results revel that Molybdenum Atomic percentage in the Nickel–Molybdenum alloy has effect on porosity and surface roughness. It was also found that root mean square value of surface roughness was not only affected by the Molybdenum Atomic percentage but also by potential at relaxation time (TOFF) potential.

Ultrafine-Grained HSLA Steel Processed Using MAF: Dry Sliding Wear and Corrosion Behaviour

As ultrafine grained (UFG) steels obtained by severe plastic deformation (SPD) are useful for structural purposes and micro devices, it is necessary to establish the relation of microstructure with wear and corrosion properties. Very few studies are available that correlate the microstructural changes and the mechanical properties of UFG steels to the degradation phenomena such as wear and corrosion. In present work a HSLA steel was severely deformed by warm (500°C) multiaxial forging (MAF) technique using up to nine strain steps. Submicron sized grain size was obtained after warm MAF. The hardness and strength improved significantly. The MAF processed UFG HSLA steel did not show any improvement in wear resistance. Low pull-off-work and fragmented nanosized pearlitic cementite particles were the two factors found responsible for it. The corrosion resistance of HSLA steel after warm MAF remained largely unaffected.