Abstract: In the manuscript conventional and nanostructured nitrided coatings developed to increase hardness and to improve the wear, erosion and corrosion resistance of structural materials. Three coatings of TiAlN were deposited on AISI-304, out of which two were thin nanocoatings at different temperatures of 500°C and 200°C are developed by Oerlikon Balzer’s rapid coating system machine under a reactive nitrogen atmosphere. One conventional coating TiAl was deposited by Plasma spraying method which was post nitrided. Then the coated samples were characterized with relative to coating thickness, microhardness, porosity and structure. The XRD and SEM/EDAX techniques have been used to identify various phases formed after coating on the surface of steel.The microhardness of conventional TiAlN coating was found to be of the order of 900-950 Hv. The grain size for nanostructured TiAlN coatings deposited at 500°C and 200°C are 15nm and 14nm respectively as calculated by Sherrer’s formula from XRD plot.
Abstract: The aim of this study is to investigate the effect of cryogenic treated electrodes on the sensitization of ‘304 SS’ in resistance spot welding (RSW). An approach to model sensitization based upon the weld properties like: hardness, tensile-shear strength (T-S), while RSW of 304SS has been proposed and applied. Relationship between hardness, T-S and other parameter has been deduced by using Taguchi L9 orthogonal array (OA). The results indicate that for sensitization; coolant flow rate (CFR), weld time and voltage contributes significantly in RSW of SS.
Abstract: In the present work TiAlN coatings were deposited by plasma spray process as titanium aluminium based nitride (Ti, Al)N coatings possess excellent tribological behaviour with respect to metal cutting and polymer forming contacts. Three coatings of TiAlN were deposited on AISI-304 grade boiler steel substrate out of which two were thin nanocoatings deposited at different temperatures of 500°C and 200°C and one conventional coating was deposited by plasma spraying. The as sprayed coatings were characterized with relative to coating thickness, microhardness, porosity and microstructure. The optical microscopy (OM), the XRD analysis and field mission scanning electron microscope (FESEM with EDAX attachment) techniques have been used to identify various phases formed after coating deposited on the surface of the substrate. Subsequently the sliding wear behaviour of uncoated, PVD sprayed nanostructured thin TiAlN coatings deposited at 500°C and 200°C and plasma sprayed conventional coated AISI-304 grade boiler steel were investigated according to ASTM standard G99-03 using pin on disk wear test rig. Cumulative wear volume loss and coefficient of friction, μ were calculated for the coated as well as uncoated specimens for 0.5, 1 and 2 m/sec sliding velocities at a constant normal load of 10 N. The worn out samples were analysed with SEM/EDAX. Wear rates in terms of volumetric loss (mm3/g) for uncoated and coated alloys were compared. The nanostructured TiAlN coatings deposited at 500°C and 200°C has shown minimum wear rate as compared to conventional TiAlN coating and uncoated AISI-304 grade boiler steel. Nanostructured TiAlN coatings were found to be successful in retaining surface contact with the substrate after the wear tests.
Abstract: In electrical discharge machining (EDM) process, electrode polarity plays an important role during machining operation. This paper addresses the issues of EDM utilizing the positive and negative tool-electrode polarity to explore the effects on the performance criteria such as material removal rate (MRR), tool wear rate (TWR), surface roughness (SR) and micro-hardness during machining of Ti–5Al-2.5Sn (GradeVI) Ti alloy. The Ti-5Al-2.5Sn alloy was machined using copper-chromium electrode with positive and negative polarity by varying the peak current and pulse-on-time, while the pulse-off-time was kept constant. The result of study suggests that reverse polarity improves the MRR, TWR, SR while normal polarity improves the surface micro-hardness. The peak current has the maximum affect on machining performance for both types of polarities. Further the migration of different elements and formation of compounds on the machined surface was investigated using EDX and XRD analysis.
Abstract: In this study parts having Open Cell Porous Regular Interconnected Metallic Structure (OCPRIMS) of cubic unit cell and OCPRIMS with inner solid core were fabricated through developed process of Rapid Manufacturing (RM) process. Two approaches were used to fabricate inner solid core i,e one by using metallic phosphor bronze powder and other by using solid phosphor bronze rod. The specimens were fabricated in accordance with ISO 3928: 1999 and subjected to tension-tension and compressive-compressive fatigue testing. The endurance limit of OCPRIMS with solid rod cored structure was found to be on the higher side in comparison to other types of specimens. The results of Scanning Electron Microscopy (SEM) and images of fractured surfaces showed the presence of voids, shrinkage cavities and pointed edges on the designed pores. They acted as stress raisers and facilitated crack initiation and propagation in the specimens.
Abstract: Ultrasonic machining is a contemporary manufacturing method usually employed for processing materials with higher hardness/brittleness such as quartz, semiconductor materials, ceramics etc. The machined surface produced by ultrasonic machining is found to be free from any surface defects (heat affected zone, cracks, recast layer, etc.) in contrast to the thermal based machining processes like; electric discharge machining, laser beam machining etc. In this article, a review has been reported on the fundamental principle of ultrasonic machining, effect of operating parameters on material removal rate, tool wear rate, surface roughness and hole quality. It also presents a brief review on micro-USM, rotary USM and hybrid methods with other processes.
Abstract: WC-Co composite materials possess a vast range of industrial applications owing to their excellent properties such as superior hardness, toughness and dimensional stability. Present article has been targeted at investigating the impact of different experimental conditions (power rating, cobalt content, tool material, thickness of work piece, tool geometry, and abrasive grit size) on penetration rate in ultrasonic drilling of WC-Co composite material. Taguchi’s L-36 orthogonal array has been employed for conducting the experiments. Significant factors have been identified using analysis of variance (ANOVA) test. The experimental results revealed that power rating, abrasive grit size, and tool profile is most significant factor for penetration rate. From the microstructure analysis, the modes of material deformation have been observed and the parameters (i.e. work material properties, grit size, and power rating) were observed as the most crucial for the deformation mode.
Abstract: In the present investigation, 75Cr3C2-25NiCr coating was deposited on T91 boiler tube steel substrate by high velocity oxy-fuel (HVOF) process to enhance high-temperature corrosion resistance. High-temperature performance of bare, as well as HVOF-coated steel specimens was evaluated for 1500 h under cyclic conditions in the platen superheater zone coal-fired boiler, where the temperature was around 900 °C. Experiments were carried out for 15 cycles each of 100 h duration followed by 1 h cooling at ambient temperature. The performance of the bare and coated specimens was assessed via metal thickness loss corresponding to the corrosion scale formation and the depth of internal corrosion attack. The uncoated boiler steel suffered from a catastrophic degradation in the form of internal oxidation attack and thickness loss. The 75Cr3C2-25NiCr coating showed good adherence to the boiler steel during the exposures with no tendency for internal oxidation.
Abstract: The purpose of this investigation is to develop a mathematical model for predicting the influence of casting parameters on hardness of non ferrous alloy (NFA) castings produces using Zcast process by employing response surface methodology (RSM). An association has been proposed between hardness of castings and shell wall thickness (SWT), weight density (WD) and pouring temperature (PT) of the shell mould fabricated using three dimensional printer (3DP). The experiments were conducted using NFA materials like; aluminium, zinc, lead, copper, brass and bronze. An effective procedure of RSM has been utilized for the optimal values of casting parameters. Mechanical Micro-Vickers hardness was measured in which the indent is produced by applying a known load to the specimen and then measuring the size of the appropriate diagonals optically. Based on experimental data the investigation has led to conclusion as Quadratic model have been established for predicting the response in the form of hardness of castings.Further, the model developed was validated by analysis of variance (ANOVA) which indicated the significance of model. The Model F-value of 2477.66 implies that the model is significant. There is only a 0.01% chance that a Model F-Value could occur due to noise. Values of "Prob > F" less than 0.05 indicate model terms are significant. The statistical analysis of second order quadratic equation results showed that the most significant parameters, favoring the hardness are B, C and A2. The superiority of the quadratic mathematical models were developed in confidence intervals of 99.75% with prediction error sum of squares of 3.6%for the prediction of the harness.Microstructure analysis was also performed for justification of hardness data.
Abstract: Modeling and optimization of machining parameters are the indispensable elements in modern metal cutting processes. The present study realize the interaction of drilling input process parameters such as spindle speed, feed rate and number of holes and their influence on the surface roughness, diameter and position of hole obtained in drilling of mild steel. The contour plots were generated to highlights the interaction of process parameters as well as their effect on responses. An empirical model of surface roughness, diameter and position of hole was developed using response surface methodology (RSM). The model fitted and measured values were quite close, which indicates that the developed models can be effectively used to predict the respective response. The process parameters are optimized using desirability-based approach response surface methodology.