Plasma spraying is used to produce wear resistant coatings. However, the primary problem is the poor bonding strength between the coating and the substrate. The secondary problem is the high porosity in the as-sprayed coatings, which reduces the wear resistance of coating. In order to overcome these problems, the sealing of plasma-sprayed coating by electrodeposition has been used. The sealing of plasma-sprayed coatings alters the wear mechanism and wear resistance. The wear mechanism and wear resistance largely depends on the applied load, sliding speed and sliding distance. Hence, an effort has been made in the present work to study the effects of these parameters on wear volume loss using response surface methodology (RSM)-based mathematical models. The experiments were conducted as per Central Composite Design (CCD). It reveals that the applied load was the most predominant factor affecting the wear volume loss of the coating material. The sliding speed is the next most important parameter influencing the wear volume loss. The wear volume loss of the sealed plasma-sprayed molybdenum coating occurs mainly due to the formation of grooves, surface tribo films, fracture of splats and delamination of the coating.

Plasma-sprayed molybdenum coatings are used in automotive, aerospace, pulp and paper industries in order to guard the machine parts against wear and corrosion. In this work, an attempt has been made to study the effect of particle size on wear behaviour of molybdenum coated steel. Two types of Mo coatings were deposited on American Iron and Steel Institute (AISI) 1020 steel substrate, one is with particle size of 15-40 mm (type I) and another one is with 40-90 mm (type II) using plasma spraying. The microstructures and worn surface morphologies of the coatings were analysed by means of X-ray diffractometer and scanning electron microscopy. It was found that the as-sprayed type I and type II coatings consist of molybdenum (Mo) as the major phase and molybdenum oxide (MoO 2 ) as the minor phases. For the evaluation of influence of coating powder particle size on wear characteristics, the sliding wear tests were performed on a pin-on-disc apparatus. The variation of volume loss with applied load, sliding speed and sliding distance was monitored. The type I sprayed coating exhibits better wear resistance. Tribological testing was also supported by metallographic examination for the identification of wear mechanisms. It was verified that the wear of coating is dominated by fracture of splats, crack propagation, delamination and plowing.

Variable displacement pumps are commonly employed in fluid power equipment. In applications involving variable displacement pumps, overheating of oil is a frequently encountered problem necessitating an effective oil cooling solution. In this work, the thermo-hydraulic performance analysis of an air blast hydraulic oil cooler, which is a compact heat exchanger (Brazed Aluminium Plate-Fin type) with surface heat enhancement feature in the form of rectangular offset strip fins is presented. The performance models available in the literature present correlations for f and j factors limited to a particular surface geometry and Reynolds number Re range. In the present work a detailed theoretical thermo-hydraulic analysis of an existing heat exchanger is presented using models available in the literature and also experimentally validated using a developed test-rig. The performance parameters derived from f and j factors like exchanger effectiveness, heat transfer coefficients and pressure drop are amply addressed. It was found that, cooler effectiveness varied only slightly with increasing oil inlet temperatures; whereas effectiveness decreased with increasing flow rates. The heat transfer rates increased with increasing oil flow rates and also with increasing oil inlet temperatures. The pressure drop on the oil side was found negligible.

Plasma sprayed molybdenum coating thickness of 300 μm was deposited on steel substrate. Electro deposition of nickel has been used to fill the open pores and micro cracks of the plasma sprayed molybdenum coating. The quantitative investigation of porosity was carried out with image analysing software. The microhardness was measured using a Vickers' indenter. The influence of sealing on wear resistance of plasma prayed molybdenum was estimated by using pin on disk wear test rig. The worn surface was characterised by scanning electron microscopy. The experimental results indicated that porosity of coating was decreased and microhardness was increased by sealing. It is concluded that electro deposition of Ni is a promising sealing treatment for sprayed coating. In this study, sealed plasma sprayed coating consisting of lowest porosity, the higher hardness and better wear resistance.Reference to this paper should be made as follows: Manjunatha S.S. and Basavarajappa, S. (2015) 'The effect of sealing on the wear behaviour of plasma sprayed Mo coating', Int.

Titanium alloys are widely used in various fields, including the medical field, the automotive and manufacturing sectors. Traditional machining processes are only useful for a limited number of tasks due to the detrimental effects they have on the strength and stiffness of the machined alloys. However, one of the most favoured post-processing equipment used to obtain a high-quality surface is the wire electrical discharge machining (WEDM) technology. The most crucial aspects of WEDM are the rates of the electrical current and voltage, in addition to the pulse-on and pulse-off durations. As a form of wire, WEDM makes use of brass wire that has been zinc-coated. The WEDM method is utilised in the machining of titanium alloy of grade 7 for this project. The surface of titanium grade 7 that had been processed using WEDM was analysed with a scanning electron microscope. The pictures revealed that the material exhibits homogenous solidification and a columnar grain structure along the build direction. As the pulse-on time gets longer, the Material Removal Rate (MRR) also gets higher. When the pulse-on time is set to 60 µs, the greatest MRR that can be achieved is 7.357 mm3/min. As the pulse-off duration gets longer, the MRR is getting lower. At a pulse-off time of 20 µs, the minimal MRR is reached, and it is equivalent to 5.935 mm3/min. At a peak current 6A, the highest MRR is measured is equivalent to 7.795 mm3/min.