Surface Properties and Corrosion Behavior of Turn-Assisted Deep-Cold-Rolled AISI 4140 Steel
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JMEPEG https://doi.org/10.1007/s11665-020-05051-x
Surface Properties and Corrosion Behavior of Turn-Assisted Deep-Cold-Rolled AISI 4140 Steel P.R. Prabhu, Deepa Prabhu, Sathyashankara Sharma, and S.M. Kulkarni (Submitted April 16, 2020; in revised form July 5, 2020) In this research, the effect of various turn-assisted deep-cold-rolling process parameters on the residual stress, microstructure, surface hardness, surface finish, and corrosion behavior of AISI 4140 steel has been investigated. The examination of the surface morphology of the turned and processed samples was performed by using a scanning electron microscope, energy-dispersive spectroscopy, and atomic force microscopy. Response surface methodology and desirability function approach were used for reducing the number of experiments and finding local optimized conditions for parameters under the study. The results from the residual stress measurements indicate that the rolling force has the highest effect by generating a deeper layer of residual compressive stress. The outcomes of surface hardness and surface finish emphasize that rolling force and number of tool passes are the most significant parameters affecting the responses. Surface studies confirmed the corrosion and its intensity onto the metal surface, and according to atomic force microscopy studies, the surface had become remarkably rough after exposure to the corrosive medium. Improvements in surface microhardness from 225 to 305.8 HV, the surface finish from 4.84 down to 0.261 lm, and corrosion rate from 6.672 down to 3.516 mpy are observed for a specific set of parameters by turn-assisted deep-cold-rolling process. The multiresponse optimization for surface finish and corrosion rate together shows that a ball diameter of 10 mm, a rolling force of 325.75 N, initial roughness of 4.84 lm, and number of tool passes of 3 give better values for the two responses under consideration with composite desirability of 0.9939. Based on the experimental work at the optimum parameter setting, the absolute average error between the experimental and predicted values for the corrosion rate is calculated as 3.2%. Keywords
corrosion rate, deep cold rolling, residual stress, scanning electron microscope, surface hardness, surface finish
1. Introduction Most of the components used in the aerospace and automobile industry require excellent surface characteristics as they work under severe conditions (Ref 1). Fatigue is one of the main reasons for the failure of these components. About 90% of all mechanical service failures are due to fatigue (Ref 2, 3). The fatigue failure relies entirely upon the ultimate strength or yield stress of the material. But actuality, different factors, for example, geometry, quality of the surface, type of material, residual stresses, loading direction, size of the grain, surrounding atmosphere, operating temperature may reduce the service life of a component (Ref 4, 5). Fatigue occurs due to cracks originated on free surfaces, and therefore fatigue life is reliant on the surface finish (Ref 6
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