Microstructure Investigation, Hot Tensile and Hot Corrosion of IN600 to Nimonic 75 heterogeneous Connection in Spot Welding

Nimonic 75 and Inconel 600 alloys are the Nickel-based superalloys which are used in manufacturing gas turbine components. In the current research, a superalloy Ni-based Nimonic sheet and Inconel 600 were used, joint by resistant spot welded (RSW) machine at currents of 2, 4, and 6 kA, pressure of 5 and 7 bar, and times of 0.6, 0.9 and 1.2. Non- destructive inception methods and light and scanning electron method (SEM) and light optic microscope (LOM) were used to evaluate joints' quality. Shear and micro-hardness test was used to check the mechanical properties of the joint. The findings indicate that the most appropriate welding connection of inhomogeneous points at the current of 4 kA was the holding time 0.9 second and electrode force 7bar. The analysis of microstructure consisted of 3 welding zones which are affected by heat and the base metal. The warm corrosion scanning microscope test results at 600 °C and 800 hours confirmed that the existence of a chromium oxide layer on the surface of the superalloy, which has the main role in protecting the piece in the output temperature.

Multi-Objective Optimization of Electro Discharge Machining of NIMONIC 75 Using Taguchi-Based Gray Relational Analysis

New superalloys are potential materials in aircraft and power plant industries because of their properties like high-temperature strength, creep life and resistance to corrosion and oxidation at elevated temperatures. Because of the superior properties of superalloys, machining them using the conventional processes is a difficult task that is associated with high cost and poor accuracy. In this study, an attempt has been made to machine NIMONIC 75 superalloy by the electro discharge machining (EDM) process, using the Taguchi-based Gray Relational Analysis method for multi-objective optimization of material removal rate (MRR), tool electrode wear rate (TEWR) and surface finish (SF). The experiments conducted were based on [Formula: see text] (2[Formula: see text]) orthogonal array. Six input parameters namely tool material, peak current, gap voltage, pulse on-time, pulse off-time and tool lift time were considered in this study. The validation results proved that the parametric setting of tool material as copper, peak current as 12[Formula: see text]A, gap voltage as 50[Formula: see text]V, pulse on-time as 200[Formula: see text][Formula: see text]s, pulse off-time as 15[Formula: see text][Formula: see text]s and tool lift time as 2[Formula: see text]s, yields optimized values of the performance characteristics. SEM images indicate the presence of numerous surface irregularities, whereas the XRD test shows the formation of various carbides on the EDMed surface.

Impact of Electrical Process Parameter in Electrochemical Micromachining of Nimonic 75 Alloy

Electrochemical micromachining is one among the widely known method for machining micro holes in electrically conductive, hard to cut materials. As nimonic 75 alloy can withstand alternate cooling and heating conditions, it finds application in aero combustor liner. In this study, solid tungsten carbide (500µm) was selected as the tool to produce micro holes in the work-piece (nimonic 75 alloy). As pulsed current, results in more confined dissolution, trials were performed by changing electrical process parameter such as duty cycle, pulse on period and pulse off period and their effect on MRR and dimensional deviation were studied. Employing TOPSIS, lower values of duty cycle and pulse on period was desirable for the production of holes with better geometrical features and the similar was found to be in concurrent with SEM images.

Optimization of WEDM process parameters in machining Nimonic 75 alloy using brass wire

PurposeAn experimental study has been conducted to model and optimize wire electric discharge machining (WEDM) process parameters such as pulse-on time, pulse-off time, servo voltage and peak current for response characteristics during machining of Nimonic 75 alloy.Design/methodology/approachThe response surface methodology (RSM)-based Box–Behnken's design has been employed for experimental investigation. RSM is used for developing quadratic regression models for selected response variables i.e. material removal efficiency and kerf width. To validate the model, confirmation experiments have been performed. The multi-response optimization has been done using desirability function approach.FindingsThrough analysis of variation, the percent contribution of process parameters on the response characteristics has been found. Pulse-off time is the most significant parameter affecting the kerf width and material removal efficiency followed by pulse-on time. The quadratic regression models have been developed for prediction of selected response variables. An attempt has been made to optimize the WEDM parameters for material removal efficiency and kerf width. The recommended process parameter setting for maximum material removal efficiency and minimum kerf width have been found to be pulse-on time = 0.6 µs, pulse-off time = 14 µs, servo voltage = 25 V and peak current = 200 A.Originality/valueThe “kerf width” is an important response variable for maintaining dimensional accuracy of the machined component, but has not been given due attention by the researchers. In the present work, the developed regression model for “kerf width” can be used in estimating wire offset setting and thereby getting a dimensionally accurate product. The optimum process parameters obtained in WEDM of Nimonic 75 alloy will contribute in database of machining. The outcome of this study would be added to scare database of the machining of Nimonic 75 alloy and also would be extremely useful for making the technology charts for WEDM.