High‐temperature corrosion behavior of some post‐plasma‐spraying‐gas‐nitrided metallic coatings on a Fe‐based superalloy

Abstract

The objective of the present study is to propose a cost-effective process for modifying commercially available coatings by gas nitriding using commonly available equipment and starting materials. Al-Cr and Ti-Al metallic coatings were deposited on Superfer 800H (Fe-based superalloy) using a plasma spray process. Then the gas nitriding of the coatings was done in the lab and the parameters were optimized after conducting several trials on plasma-sprayedcoated specimens. Characterization and high-temperature corrosion behavior of coatings after exposure to air and molten salt at 900°C were studied under cyclic conditions. Techniques like XRD, SEM/EDX, and X-ray mapping analysis were used for the characterization of the coatings and analysis of the oxide scale. Both the coatings successfully protected the substrate and were effective in decreasing the corrosion rate when subjected to cyclic oxidation (Type-I hot corrosion) at 900°C for 50 cycles in air and molten salt (a salt mixture of Na 2 SO 4 -60%V 2 O 5 dissolved in distilled water). Based on the findings of the present study, the coatings under study are recommended for tapplications to super-heater and reheater tubes of boilers and all those surfaces that face fireside corrosion, such as fluidized beds, industrial waste incinerators, internal combustion engines, gas turbines or steam turbines, to provide protection against degradation in these environments. The cost of the product/process is approximately Rs. 0.62 per mm 2 in case of Al-Cr coating and Rs. 1.86 per mm 2 in case of Ti-Al coating.

Isothermal oxidation behavior of W‐free Co–Ni–Al‐based superalloy at high temperature

“…The oxidation products were mainly irregularly discrete oxides at 1073 K. However, entirely different oxides with large particle sizes are transformed with increasing temperature to 1173 K as shown in Figure 2b,d. Moreover, there was no significant difference of oxides morphologies on the surfaces of 2Cr and 2Mo oxidized samples at 1173 K. The significantly different morphologies with different temperatures can be certainly attributed to the grain size of the CoO/Co 3 O 4 oxide dependent on exposed temperature, which has been confirmed by Weiser et al [ 35,36 ]…”

Microstructure and atmospheric oxidation behavior of CrCuFeMnNiCox high‐entropy alloys fabricated by vacuum hot‐press sintering

“…At present, the relatively mature superalloys mainly include Ni-based, Co-based, and Fe-based superalloys. [1][2][3][4] The Ni, Co, and Fe contents in these superalloys are more than 50 wt.%, and other solid solution strengthening elements, such as Cr, Ti, Al, Mo, W, Nb, Zr, B, Y, and Ce, can be added to improve the high-temperature strength, oxidation resistance, and hot corrosion performance of the alloys. However, the content of Ni, Co, and other precious metals in the alloys is high, which is not conducive to reducing production costs.…”

Degradation Processes in the Ai-Ti-Si System Under Thermal Shock

“…As a result, starting from a certain integration level of semiconductor devices, signal delays in the interconnections may exceed those in the structures themselves. In addition, as the semiconductor cross-sections decrease, the problems appear that are related to electromigration in thin metal films and contact ohmicity (Kang et al, 2008;Martineau et al, 2014;Macherzyński et al, 2016;De Rose et al, 2018;Homa and Sobczak, 2019;Eslami et al, 2019;Fischer et al, 2019;Chawla et al, 2019;Cruz et al, 2019;Yi et al, 2019). And technological complexities when making modern metallization systems (including the structures involving p-n junctions with small occurrence depth) should also be noted (Garosshen et al, 1985;Macherzyński et al, 2016).…”