Finite Element and Experimental Analysis of Residual Stresses in Electron Beam Welded Nickel-Based Superalloys

In this paper, two different nickel-based superalloys, namely Inconel 718 and Nimonic 80A were joined using electron beam welding techniques with three different welding parameters. A finite element analysis (FEA) using Abaqus software was carried out to calculate the residual stresses due to welding. Both transverse and longitudinal residual stresses were determined. Also, an X-ray residual stress measurement system, μ-X360 Ver. 2.5.6.2 was used for measuring transverse residual stress along and across the weld centerline. The transverse residual stress found by FEA and that measured experimentally was nearly the same thus validating the FEA. Also, the peak values of longitudinal residual stress found using the FEA were close to the yield strengths of the base metals as found elsewhere.

Growth Kinetics and Some Mechanical Properties of Plasma Paste Borided Layers Produced on Nimonic 80A-Alloy

Plasma paste boriding was employed in order to produce the boride layers on Nimonic 80A-alloy. The process was carried out at temperatures of 1023 K, 1073 K and 1123 K for 3, 4 and 6 h in a gas mixture of 50% H2-50% Ar. Borax paste was used as a boron source. The microstructure of the produced surface layers consisted of the mixture of nickel borides and chromium borides. The effect of processing temperature and duration on the thickness of the borided layers was observed. The theoretical thicknesses of the borided layers were estimated using an integral diffusion model. A good correlation was obtained between the theoretical (modeled) and experimental depths of the plasma paste borided layers. The boride layers were characterized by a high hardness ranging from 1160 HV to 2132 HV. The multiphase character of the produced layers resulted in differences in hardness. A significant improvement of the wear resistance of the plasma paste borided Nimonic 80A-alloy was observed in comparison with the non-borided alloy.

Grinding of High-Strength Materials

The joint research of scientists of two countries deals with cylindrical and surface grinding with abrasive wheels of heat-resistant steel Inconel 625 (KhN77TYu GOST 5632 – 72 Russian Federation standard), (analogues include Hastalloy, N07080, Alloy 80A, Nimonic 80A, 2.4952 ASTM B637/ASME SB637, UNS N07080). The article shows the results of studies of the features of high-temperature steel during grinding with a fastened abrasive. The results of experiments are given to determine the optimal characteristics of grinding wheels, grinding modes, cooling-lubricant fluids. Experimental data about geometric accuracy, surface roughness, resistance of wheels are demonstrated as well. The ways to prevent from defects during cylindrical and surface grinding of high-strength steel are proposed. The recommendations to increase the tool resistance and output of the process are given.

Finite Element Simulation of Friction Stir Welding of Inconel 718 to Nimonic 80A

This paper presents results of simulation of friction stir dissimilar welding of 5 mm thick, Nickel-based super-alloys, Inconel 718, and Nimonic 80A using Abaqus software. Four different trials were done to understand the influence of tool rotation speed on temperature distribution in weld zone while travel speed remains constant. The temperature in the weld zone was found to increase with the increase in tool rotation speed and travel speed. The temperature on the advancing side of the tool was higher than that of the retreating side. The tensile strength of weldment was found, by simulation, to be 25% more than that of base metal, Inconel 718. This may be due to grain refinement and dynamic recrystallization during FSW. The simulated bend test revealed an adequate level of ductility of weldments.

Evaluation of machining performance and multi criteria optimization of novel metal-Nimonic 80A using EDM

This study focused to machine novel Nimonic 80A through Electric Discharge Machine process. The process parameters are optimised to achieve high surface integrity along with high material removal rate (MRR) with minimum energy consumption. Central composite design along with analysis of variance technique has been applied to make correlation between the process parameter and responses. The developed model of surface roughness shows that the peak current and pulse-on time have significant effect whereas; a little effect of pulse-off time. The said result may be obtained due to simultaneous action of deposition and notching (removal) of material in order to form crater. In case of MRR, the pulse-on time and peak current are found as significant factors with increasing trend (i.e. when the input values are increased the MRR increases) whereas; a reverse trend is noticed with pulse-off time. The optimum values for maximum MRR (0.512444 gm/min) and minimum surface roughness (7.82203 µm) with 81% desirability are obtained for the process parameter as 13.49 A peak current, 150 µs pulse-on time and 4 µs pulse-off time.