Quantifying Thermal Spray Coating Architecture by Stereological Protocols: Part I. A Historical Perspective

This article presents, from a historical perspective, some stereological protocols of the first order. Such protocols can be implemented to quantify statistically the architecture of thermal spray coatings and their relevant features (pores, lamellas, etc.). A forthcoming Part II of this article will address some key points to implement, from a practical point of view, such protocols.

Modeling Microstructural Evolution During Dynamic Recrystallization of Alloy D9 Using Artificial Neural Network

An artificial neural network (ANN) model was developed to predict the microstructural evolution of a 15Cr-15Ni-2.2Mo-Ti modified austenitic stainless steel (Alloy D9) during dynamic recrystallization (DRX). The input parameters were strain, strain rate, and temperature whereas microstructural features namely, %DRX and average grain size were the output parameters. The ANN was trained with the database obtained from various industrial scale metal-forming operations like forge hammer, hydraulic press, and rolling carried out in the temperature range 1173-1473 K to various strain levels. The performance of the model was evaluated using a wide variety of statistical indices and the predictability of the model was found to be good. The combined influence of temperature and strain on microstructural features has been simulated employing the developed model. The results were found to be consistent with the relevant fundamental metallurgical phenomena.

Evolutionary and Genetic Algorithms Applied to Li<Superscript>+</Superscript>-C System: Calculations Using Differential Evolution and Particle Swarm Algorithm

A set of empirical potentials based upon two and three body interactions were constructed for the Li⁺-C system and structural optimizations for various assemblages containing Li⁺ ions and graphene sheets were conducted using some emerging evolutionary and genetic algorithms, differential evolution, and particle swarm optimization in particular. Some limited molecular dynamics calculations were also performed. The results are discussed and analyzed with reference to the lithium ion batteries, where the graphite-Li⁺ assemblages traditionally constitute the negative electrode, for which the present results are highly pertinent.

Influence of Suspension Plasma Spraying Process Parameters on TiO2 Coatings Microstructure

The study aimed at optimizing the suspension plasma spraying of TiO₂ coatings obtained using different suspensions of fine rutile particles in water solution onto aluminum substrates. The experiments of spraying were designed using a 2³ full factorial plan. The plan enabled to find the effects of three principal parameters, i.e. electric power input to plasma, spray distance, and suspension feed rate onto microstructure of coatings, content of anatase phase and size of anatase crystals in the coatings. The microstructure of deposits was observed with scanning electron microscope (SEM) and optical microscope and their composition was characterized using energy dispersive spectrometry (EDS). The observations were made on the coatings surface and their cross-sections. The latter made it possible to determine the coatings thicknesses to be in the range from 8 to 33 μm.

Characterization of the Micro-Welding Process for Repair of Nickel Base Superalloys

Micro-welding is a low-heat input process whereby a metal or cermet, is deposited by the generation of a low-power arc between a consumable electrode and a substrate. The low-heat input of this process offers unique advantages over more common welding processes such as gas tungsten arc, plasma arc, laser, and electron beam welding. At present, the repair of turbine blades and vanes commonly involves gas tungsten arc welding and these components are susceptible to heat affected zone cracking during the weld repair process; vacuum brazing is also used but mainly on low-stress components such as stators. In this study, the low-heat input characteristic of micro-welding has been utilized to simulate repair of Inconel (Trade Mark of Special Metals) 625, Inconel 718, and Inconel 722 filler alloys to a cast Inconel 738 substrate. The effect of micro-welding process parameters on the deposition rate, coating quality, and substrate has been investigated.

Equilibrium Phase Diagram of the Ternary 2-Nitrobenzoic acid-3-Nitrobenzoic Acid-Acetone System at 283.15 K and 313.15 K

In this investigation, the mutual solubilities for ternary 2-nitrobenzoic acid-3-nitrobenzoic acid-acetone system were measured at 283.15 K and 313.15 K, respectively. Two partial isothermal phase diagrams of the system were constructed on the basis of the measured solubilities, one at 283.15 K and the other at 313.15 K. The phase diagrams of the ternary system are similar at the different temperature. Two solid phases were formed and confirmed by the Schreinemaker’s wet residue method, and the two were identified as 2-nitrobenzoic acid and 3-nitrobenzoic acid. The crystallization regions of 2-nitrobenzoic acid and 3-nitrobenzoic acid increase as the temperature decreases.

High-Temperature Corrosion in Waste-to-Energy Boilers

There are 88 waste-to-energy (WTE) plants in the U.S. and over 600 worldwide. In total, they combust close to 143 million metric tons of municipal solid wastes (MSW) and generate about 45 billion kW · h of electricity and an equal amount of thermal energy for district heating and industrial use. The presence of various impurities, especially HCl and chloride salts, in the combustion gases results in much higher corrosion rates of boiler tubes and has led to the development of special alloys and also metal protection techniques, including high velocity oxygen fuel (HVOF) sprayed coatings. This study examines the corrosion mechanisms in WTE boilers and summarizes the findings of a corrosion survey of several WTE facilities in the U.S. The study also examines existing and potential methods for reducing corrosion problems.

System identification during milling via active magnetic bearing

One of the main focuses of recent machine tool development is to increase the machining performance. But the enhancement of the metal removal rate (MRR) is often limited by the stability of the milling process. To prevent unintentional chatter vibrations and to observe changes in the system’s behavior, there is a need to observe the state of the milling process during machining. Beside others, one approach is the development of an adaptronic motor spindle using active magnetic bearings (AMB) combined with conventional roller bearings in a so called “hybrid approach”. The AMB acts as a contact less sensor and actuator, in order to estimate the frequency response function (FRF) of the spindle-tool system during the milling process. The two major dependencies on the FRF are the spindle speed and the cross-sectional area of the chip. Also the closed loop damping can be observed to estimate the stability margin. This paper presents the identification of the varying eigenvalues during the machining.

Evaluation of Advanced Adhesives for Aerospace Structures

Polymer adhesives are finding increased use in panel joining applications in aircraft and aerospace structures where the applied stresses permit their use and where a uniform stress distribution is needed. One such adhesive, Hysol EA-9394™, was compared to three other formulations in this study. The new formulations were Hysol EA-9396, Hysol EA-9396 filled with nickel nanofibers and mixed by machine (Jamesbury Blender), and Hysol EA-9396 filled with nickel nanofibers and hand mixed in the laboratory. The comparison consisted of measuring shear lap strengths of aluminum test pieces bonded together with the candidate adhesives. The mechanical tests were supplemented by a Weibull analysis of the strength data and by a visual inspection of the failure mode (adhesive/cohesive). The lap shear strengths (fracture stress values) of all three Hysol EA-9396 adhesives were greater than that of the baseline Hysol EA-9394 polymer.

Effect of heat treatment on the structural transformations and properties of high-nitrogen chromium steels

Conclusions