Improvement in corrosion resistance of Inconel 718 for turbines
Inconel 718 superalloy is commonly used in gas turbine engineering, submarine, nuclear reactors, oil and gas production components as it provides suitable performance. In ship gas turbine and submarine which mainly work in the marine condition, the performance of Inconel 718 should be properly evaluated to find suitable countermeasures for the safety of operation system. Additionally, good corrosion resistance is advantageous to the service life of the components due to cracks initiation at the material’s surface. Corrosion performance is mainly affected by chemical composition of material and its surface states like hardness and surface stress. High nickel alloy Inconel 718 has strong resistance to chloride stress cracking corrosion. Simultaneously, due to the presence of chromium, it offers superior corrosion resistance than pure nickel in the oxidizing condition. The performance of Inconel 718 wire in electrochemical machining, states that the produced niobium carbide and niobium oxide have a significant effect on the corrosion process of nickel based superalloy. Hydrogen permeation of Inconel 718 in different states is evaluated and it is noticed that hydrogen trapping in cold rolled and precipitation hardened Inconel 718 is irreversible.
The effect of chemical elements on the corrosion performance of alloy is evaluated. Additional influential factors should also be evaluated to enhance corrosion performance.
To improve the corrosion resistance of nickel based superalloy, different processing methods were used. The improved corrosion function of Inconel 600 is noticed through laser shock peening. Larger and deeper compressive residual stresses and smaller surface roughness are the major factors for the improved corrosion resistance.
Electrochemical corrosion resistance of Inconel 718 sheets processed by electron beam welding in 3.5% NaCl solution. To decrease the vigorous impact on corrosion resistance, an approach of subsequent heat processing is following. The results of function of Inconel 718 in simulated body fluid state that laser surface modified process can improve the corrosion resistance of materials suitably. The change in impingement angle to evaluate the corrosion resistance of nickel based superalloy after laser surface treatment is evaluated. It was found that corrosion resistance is improved by 1.5 times due to reduction of energy transfer of laser. It is an applicable process to enhance erosion resistance under the parameter of ensuring efficiency. Laser material deposition and laser surface processes for complete manufacturing of Inconel 718 components. The surface quality was enhanced and roughness was decreased.
The effect of surface roughness on the corrosion behavior of Inconel 718 is a simulated marine condition at high temperature for a comparatively long time. Although the mechanism of residual stress affecting corrosion nickel based super alloys has not been evaluated yet.
Inconel 718 hot forging slate annealed at 980oC for 10 minute and then air cooled. The materials were then acid pickled. The acid solution comprised 10% HNO3 + 7% HF. The acid pickling is used to remove the oxide produced on the surface of the material during heat processing. Ultimately, the corrosionresistance of material improves remarkably.