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The oxidation behaviour of a wrought Ni‐Mo‐Cr alloy was studied under thermal cyclic conditions in air at 800°C for exposure periods of up to 1,000 h. The morphologies, microstructures and compositions of the oxide scales were characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy and X‐ray diffraction. Oxidation kinetics were determined by weight gain measurements. Results show that steady‐state oxidation was achieved within 1 h of exposure while partial scale spalling was observed after 400 h. The alloy grain boundaries intersecting the alloy surface showed preferential oxidation. They became depleted in Ni and enriched in Mo and Cr during transient oxidation. The scale initially formed at the surface was NiO which grew outwardly and laterally to cover the entire alloy. Upon continued oxidation, the scale developed into an outer NiO layer and an inner Cr₂O₃ layer while the presence of NiMoO₄ was also observed within the scale.

To determine if the interim use of liquid waste as a fuel in a catalytic steam reformer unit had any deleterious effect on the long‐term life of the reformer tubes.

Standard metallographic techniques were used to prepare representative samples obtained from various sections of the reformer tubes for metallurgical evaluation. Microstructural characterization was carried out in a scanning electron microscope equipped with an energy dispersive X‐ray spectrometer. Imaging and elemental analysis was used for the identification of the alloy material, corrosion products and other microstructural features.

Hydrogen was produced in a catalytic steam reformer by cracking methane using natural gas as a fuel. Corrosion of reformer tubes occurred when natural gas fuel was replaced with a liquid waste. Use of liquid fuel waste accelerated the rate of oxidation at the outer tube surface. However, foreign species from the fuel were not transported into the tube material. The heat‐resistant steel casting used for this application was susceptible to precipitation of Si‐stabilized Ni‐Nb Laves phase, thus reducing rupture life of the component. Voids at grain boundaries indicative of creep damage were observed.

Although, the interim use of liquid waste fuel appeared not to have damaged the tubes, it was concluded that the expected service life of the tubes may not be realized because of the susceptibility of the material to precipitation of Laves phase. An Fe‐base superalloy UNS N08810 or UNS N08811 was recommended as a replacement material for this application.

This paper provides an account of a failure analysis study. It identifies incorrect materials selection for a particular application and suggests better alternative along with its justification. The information is deemed useful for plant designers and engineers working in the related industry.

The purpose of this paper is to study a new liquid-phase assisted texture treatment method to improve the tribological properties of 304 stainless steel.

Three groups of textured type (KY, KJ and YJ) were prepared on 304 stainless steel surface using laser circular and cross scanning method in air and liquid assisted condition. The surface morphology and element content of test samples were measured with scanning electron microscope, energy spectrum. Then, the tribological test was carried out using MWF-500 reciprocating friction and wear testing machine under dry and oil lubrication condition.

The experimental results showed that the textured surface of laser processing in air was obviously blackened, and the oxygen content was increased from 16.9% to 24%. These cases did not occur on liquid-assisted laser textured surface, which induced a better wettability and surface texture processing quality. For friction test, the friction coefficient of cross-scanning textured surface prepared in assisted liquid (YJ) was the smallest. It is reduced by 55% in oil lubrication case compared to the original surface (YS). The cross-scanning textured surface prepared in air (KJ) was a little worse in friction coefficient and a little better in wear quantity than the cross-scanning textured surface prepared in assisted liquid (YJ). It is indicated that the laser processing surface with assisted liquid has obvious advantages in surface texture quality and interfacial tribological property. The main reason is that the assisted liquid plays a role in cooling and protecting action of the machined surface. The bubbles, generated at the solid–liquid interface because of the laser heat effect, scatter the laser beam and carry out the processed melt meanwhile. The lubricating medium is easier to penetrate and store in the contact interfaces because of the higher surface textured performance and wettability.

The main contribution of this work is in providing a new surface texture processing method that has a better surface micropits quality and interfacial tribology regulation ability.

The purpose of this paper is to obtain a single setting (optimal setting) of various input parameters of pack cementation process, i.e. halide salt activator, powder of master alloy and wt% of Y₂O₃ to obtain a single output characteristic as a whole namely resistance of hot corrosion for T91 steel.

The multi-criterion methodology based on Taguchi approach and utility concept has been used for optimization of the multiple performance characteristics namely hot corrosion rate K_P1, K_P2 and K_P3 for pack cementation coated T91 steel in chlorine and vanadium environment.

All the three pack cementation parameters, namely, halide salt activator, powder of master alloy and wt% of Y₂O₃ had a significant effect on the utility function based on analysis of variance for multiple performances. The percentage contribution of halide activator (1.54 percent), master alloy powder (4.66 percent) and wt% Y₂O₃ (93.79 percent). The results indicated the beneficial influence of yttrium on the chemical stability of the protective layer in presence of chlorine and vanadium environments. The optimal parameter settings obtained in this study is A2B2C1, i.e. halide salt activator (NaCl), powder of master alloy (92Cr-8Al) and 1wt% of Y₂O₃.

The outcome of this study shall be useful to explore the possible use of the developed coating for high temperature components. Unfortunately, the pack cementation was normally limited by the diffusion and reaction kinetics involved, which has a detrimental effect on the mechanical properties of work pieces. Therefore, reducing pack cementation temperature is required for widespread application of the pack coatings.

Pack coating at optimum conditions can be used for surface coating technologies to economically improve high temperature oxidation, corrosion resistance of components.

The multi-criterion methodology based on Taguchi approach and utility concept has been used for first time for parametric optimization of wt% Y₂O₃ modified chromium- aluminide coatings for T91 steel.

In this paper, a review of materials selection methods is presented. It initially discusses the importance of materials selection in various fields of scientific study particularly in engineering design. Various tools and methods for the selection of materials are reviewed. These include materials handbook, materials data‐bases, materials selection charts, artificial intelligence systems, and other computeraided materials selection systems.