Corrosion Characteristics of Copper-Added Austempered Gray Cast Iron (AGCI).

Asiful H Seikh,Amit Sarkar,Manojit Ghosh,Jitendra Kumar Singh,Nabeel Alharthi,Sohail M A Khan Mohammed

doi:10.3390/ma12030503

Abstract

The aim of this investigation was to assess the corrosion behavior of gray cast iron (GCI) alloyed with copper. Alloyed GCI specimens were austempered isothermally at varying temperatures. After austenitizing at 927 °C, the samples were austempered at different temperatures ranging from 260 to 385 °C with an interval of 25 °C for 60 min. As a result, these samples developed an ausferrite matrix with different percentages of austenite. The resulting microstructures were evaluated and characterized by optical microscope (OM), scanning electron microscope (SEM), and X-ray diffraction (XRD). The corrosion characteristics were determined using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) of these samples. These tests were carried out in a medium of 0.5 M H2SO4 and 3.5% NaCl solution. It was observed from the potentiodynamic polarization results that with increasing austempering temperature, the corrosion rate decreased. All results of the EIS were in accordance with a constant phase element (CPE) model. It was found that with an increase in austempering temperature, the polarization resistance (Rp) increased. The austenite content was also found to influence the corrosion behavior of the austempered gray cast iron (AGCI).

Highlights

Gray cast iron (GCI) is a potential engineering material, which has a diverse range of applications including use in sophisticated automotive parts [1]
The as-cast specimens were austempered for 60 min and the resulting changes in the microstructure are presented in Figures 4a–f and 5a–f using an optical microscope (OM) and scanning electron microscope (SEM), respectively
We can see that the effect of the austempering temperature on the microstructure of austempered irons was significant

Summary

Introduction

Gray cast iron (GCI) is a potential engineering material, which has a diverse range of applications including use in sophisticated automotive parts [1]. The wide applications of GCI are possible due to its unique properties such as good thermal conductivity, relatively low melting temperature, high damping capacity, and excellent castability [1,2]. The damage of the GCI components at the exterior parts through electrochemical corrosion has been the predominant restricting mechanism against enhancing its life span [3]. Materials 2019, 12, 503 with the help of alloying additions with the aim of modifying the microstructure from ferrite to fine pearlite. It is well known that single-phase microstructures like austenite, ferrite, and martensite perform better in corrosive media compared to two-phase mixtures like bainite, pearlite, and tempered martensite [6]

Methods

Results

Conclusion