Materials Science Forum Vol. 808

Abstract: In present study, an attempt was made to reduce the erosion rate of the Pulverized coal burner nozzle material. For better resistant to erosion, material was hardfaced by Gas Metal Arc Welding (GMAW) by using solid wire electrode and flux cored wire electrode under same welding conditions. The substrate steel hardfaced with flux cored wire electrode resulted in high microhardness as compare to solid wire electrode. The erosion study was conducted, using an air jet erosion test rig at a particle velocity of 50 m/s. Ductile erosion behavior is observed in the case when the substrate steels is hardfaced with solid wire whereas brittle erosion behavior is observed when the substrate steels is hardfaced with flux cored wire. At a low angle of impingement, the abrasive type cutting is the dominating factor for material removal, and at a higher angle of impingement, impact-type as well as abrasive-type cutting actions play critical roles. Plastic deformation characterized by pitting and cutting action was also observed. Scanning electron microscopy (SEM) technique was used to analyze the eroded surface. It was concluded that damaged surfaces of Pulverized coal burner nozzle material can be successfully hardfaced and improvement in erosion resistance was observed.

Abstract: In the existing literature, the effect of various process parameters of Bore Honing on some of the quality characteristic has been reported, but the information as to how these parameters interact with each other during the operation is inadequate. Therefore, it is required to study the combined effect of the input process parameters on the performance of honing operation in order to develop parametric relationships. In the present paper, parametric relationships have been developed between three input process parameters namely, Reciprocating Speed, Over-run, and Rotational speed and three response parameters i.e. Taper, Out of Roundness, and Surface finish by the application of Response surface methodology (RSM). Strong interaction was observed between various input parameter while affecting the performance of the process. The study of response surfaces revealed some interesting facts about Bore Honing Process.

Abstract: The present experimental study has been focused to evaluate surface characteristics of cryogenically-treated (shallow/deep) tool-electrodes using powder mixed electric discharge machining. Due to the continuously growing demand of complex and precise parts, tool-electrodes have its own importance, because quality of the machined parts depends upon the surface quality of electrode. On the analogy, eighteen experiments were performed based on L₁₈ orthogonal array of Taguchi’s methodology, which consist eight input parameters. Analysis of variance (ANOVA) was employed to designate the level of significance of input parameters. Electrode material has maximum influence followed by the current and pulse on-time on electrode finish. The combination of optimum factor’s level of identified parameters was determined using Taguchi’s technique for single response. Confirmation experiments were conducted using suggested optimal parameters with its respective level to minimize the tool-electrode surface roughness. Surface characteristics of tool-electrodes were analyzed using Scanning Electron Microscope (SEM) and Energy Dispersive Spectrograph (EDS) followed by X-ray diffraction (XRD) on selected samples. The results exposed that significant material transfer from workpiece and powder mixed dielectric fluid in compound form on the tool surface.

Abstract: Nimonic-80A is a nickel based super alloy which is specifically used in aerospace industry for its high strength to weight ratio and corrosion resistance. This paper presents the influence of process parameters of wire cut Electrical Discharge Machining (WEDM) during the machining of Nimonic 80A with brass wire as electrode and optimization of machining parameters on kerf width. Process parameters (pulse-on time, pulse-off time, peak current, spark gap set voltage, wire feed and wire tension) have been investigated using L₂₇ orthogonal array. With the assistance of Taguchi quality design, ANOVA and F-test, significant parameters affecting the kerf have been identified. The surface topography of machined samples has been studied in correlation with the rate of input energy into the spark.

Abstract: This paper investigates the wire wear phenomena during finish cutting operation of wire electrical discharge machining for commercially pure titanium. In this research work, the effects of key process parameters such a wire type (zinc coated and uncoated brass wire), pulse on time (T_on), pulse off time (T_off), peak current (IP), wire feed (WF), servo voltage (SV) and wire offset (W_off) were investigated on wire weight consumption (eroded weight of wire after machining) in finish cut operation followed by rough cut WEDM. Experimental data were collected based on the Taguchi method of experimental design using L18 Taguchi standard orthogonal array. The experimental results were analyzed by conducting ANOVA test for finding out significance of the input parameters on wire weight consumption. Single response optimization was performed for exploring the optimum parametric setting for wire consumption in trim cut WEDM operation. Comparative study for the surface characteristics of the both types of wire (uncoated and zinc coated brass wire) used was done with the help of scanning electron microscopy (SEM).

Abstract: This article aims to present a review on the machining of tungsten carbide-cobalt composite material. WC-Co based materials are extensively used where the demand for high performance materials exists because these have the distinguished set of properties such as high hardness, superior wear resistance, high mechanical strength and good dimensional stability. Due to these excellent properties, it serves most applications in the field of tool and die making. Machining of the WC-Co materials is very difficult with conventional machining processes and results in poor surface finish, low material removal rate, high machining cost. Among all non-conventional machining processes, thermal energy based processes such as Electrical discharge machining, Wire EDM are most widely used to machine these materials. The machining of WC-Co is also affected by various factors such as the cobalt content and grain size and presence of other carbides. This paper attempts to critically review all these aspects of the machining of WC-CO composites.

Abstract: The purpose of this paper is to develop mathematical model to investigate the influence of shell casting parameters. Three input parameters such as shell wall thickness (SWT), Pouring temperature (PT) and weight density (WD) were selected to give output in the form of average outer diameter (AOD) as dimensional accuracy. After identification of component, technological prototypes were produced. In this work three dimensional printing (3DP) has been used as rapid shell casting to make shell mould by using Zcast 501 powder with different shell wall thickness for six different light alloy materials. Measurements on a coordinate-measuring machine helped in calculating the dimensional tolerances of the castings produced. For obtaining tight casting tolerances the dimensional accuracy of component is the most important element. The thickness, curing time and orientation of the shell molds, play an important role in providing a high quality of the cast part in time. The dimensional accuracy was found to be more in the case of maximum layer thickness and horizontal position of the component. The investigation has led to conclusions as the Quadratic models were developed for the response. The F - value is 23.93, which implies that the model as well as lack of fit is significant. The value of Prob > F is less then the standard value 0.05, which indicates model terms are significant. With the help of Post curing, shell Mold temperature was not found to affect the dimensional accuracy of the castings, significantly. It was observed that high pouring temperatures also produced castings with better dimensional accuracy. This study will provide main effect of the inputs on average outer diameter as dimensional accuracy in three dimensional printing of light alloys castings. Statistically in this case B, C, A², B², C², AB, BC is the model terms which contributes significantly to the model developed for dimensional accuracy.

Abstract: Six sigma is well known approach for process improvement using powerful statistical and engineering analysis tools. The paper presents a case study of Six sigma DMAIC methodology case study in the foundry shop of a vendor of automobile original equipment manufacturer. The authors have analyzed the casting process in detail and recommended the findings based on the case study. The authors have emphasized significance of each phase of DMAIC methodology and recommended that commitment of top management is very vital for successfully implementing six sigma projects. The authors have further recommended that management should decide that quantum of efforts and resources to be dedicated for a specific six sigma project.

Abstract: Conventional investment casting is one of the old manufacturing processes. It involves expensive tooling for making sacrificial wax patterns to make ceramic moulds. However, with the emergence of rapid prototyping technologies, now it is possible to make and use plastic patterns instead of wax patterns along with some advantages. In this paper, plastic patterns have been prepared by using fused deposition modeling and used for investment casting process. A case study has been discussed to make a biomedical implant by the hybridization of fused deposition modeling with investment casting. Dimensional accuracy, surface finish and hardness of the casted biomedical implants have been tested and reported.