Influence of alloying elements on the corrosion properties of steels during plasma nitriding process

Plasma nitriding has potential as an industrial process to improve the wear, fatigue and corrosion resistance of steels. It is well known that the corrosion properties of stainless steel deteriorate when treated with temperatures above 450°C. This is because the chromium-alloying element, which is responsible for protection against corrosion, gets converted to chromium nitrides at these temperatures. Whereas low alloy steels and high alloy steels exhibit better corrosion resistance. This is due to the presence of iron nitrides and few chromium nitride phases. In this study an attempt is made to study the effect of alloying elements on the corrosion properties of EN 8 (AISI 1045), En 24 (AISI 4340), AISI H13 and AISI 304 steels during plasma nitriding. The effects of plasma nitriding on corrosion were investigated by performing potentiodynamic tests on untreated and treated steels. The phases responsible for the improvement in corrosion resistance were detected by X-ray diffractometer. It was found that low alloy steels performed better compared to the other steels because of the presence of Fe4N, Fe3N and other nitrides, which form a dense protective layer responsible for corrosion resistance

Effect of frequency on the properties of plasma nitrided AISI 4340 steel

The paper presents the results of investigations of the structure and corrosion resistance of AISI 4340 steel after plasma nitriding with 10 kHz and 30 kHz pulse frequencies. Properties of the nitrided layer were analysed by using Scanning Electron Microscope (SEM), X-Ray Diffractometer (XRD) and micro-Vickers hardness tester. Corrosion rates were monitored through polarisation resistance technique using 3% NaCl solution. In our present work, it was found that plasma nitriding with 30 kHz frequency gave better corrosion resistance and higher surface hardness than 10 kHz on AISI 4340 steel

Heterostructure CuO/Co₃O₄ Nanocomposite: An Efficient Electrode for Supercapacitor and Electrocatalyst for Oxygen Evolution Reaction Applications

Earth-abundant transition metal oxides (TMOs) are promising electroactive materials for electrochemical energy conversion and storage applications due to their high theoretical specific capacity, enhanced electrocatalytic activity, and mechanical durability. However, the limited cycle stability and low conductivity of TMOs remain challenging for practical application. Herein, we developed a TMO-based nanocomposite of CuO/Co3O4 via precipitation followed by the microwave hydrothermal method and used as a bifunctional electroactive material for supercapacitor and oxygen evolution reaction (OER) applications. The CuO/Co3O4 nanocomposite electrode exhibits a high specific capacity of 586 C g–1 and an excellent cyclic reversibility of 113.6% under a high current density of 20 A g–1 after 5000 cycles. Apart from the high redox properties, the strong synergistic interaction between CuO and Co3O4 significantly enhances the electrocatalytic property of the material. On continuous electrolysis in 1 M KOH solution, the OER electrode fabricated with CuO/Co3O4 nanocomposite demonstrated a moderate overpotential (ηO2) of 270 mV at j = 10 mA cm–2, a slight Tafel slope of 54 mV dec–1, and significant OER stability. These results highlight the fabrication of high-performance TMOs-based CuO/Co3O4 nanocomposite and their utilization in electrochemical energy storage and conversion devices for attaining maximum efficiency