Corrosion Behavior of IN-800 Superalloy in Waste-Incineration Environments: Hot Corrosion by Molten Chlorides

The corrosion resistance of the IN-800superalloy in contact with a molten mixture of (52-48)mol.% PbCl₂-KCl, similar to that found inwaste-incineration plants, has been studied. Thecorrosion kinetics have been analyzed using continuous-currentelectrochemical techniques and electrochemical-impedancespectroscopy (EIS). Studies were performed to determinethe influence of temperature and of the presence of carbon in the salt on the corrosion rate.Scanning electron microscopy (SEM) and electron probemicroanalysis (EPMA) were used as additional techniquesto analyze the corrosion products in order to elucidate the corrosion mechanism.     

Friction and wear behaviour of β-silicon nitride–steel couples under unlubricated conditions

Abstract

The friction and wear behaviour of colloidally processed and pressureless sintered β-silicon nitride (Si₃N₄) ceramics against steel DIN Ck45K under unlubricated condition were investigated using a pin on disk tribometer. β-silicon nitride (Si₃N₄) ceramics consolidated by slip casting from suspensions with different solid loading have been studied, aiming at increasing the use of β-Si₃N₄ as cutting tools in industrial applications. The morphology of the worn surfaces of β-silicon nitride ceramics was analysed by scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). Under the conditions used, it was found that β-Si₃N₄ ceramics exhibited a low wear rate (10^?6 mm³ N^?1 m^?1) and the frictional behaviour of β-Si₃N₄ ceramics–steel couples depended on a metallic layer transferred from the steel disk to the β-Si₃N₄ ceramic pin.     

Tensile stress–strain and work hardening behaviour of 316LN austenitic stainless steel

Abstract

The true stress (σ)–true plastic strain (?) data of a type 316LN austenitic stainless steel tested at nominal strain rates in the range 3×10^-5–3×10^-3 s^-1 and temperatures of 300–1123 K were analysed in terms of flow relationships proposed by Hollomon, Ludwik, Swift, Voce, and Ludwigson. The applicability of the particular flow relationship is discussed in terms of ‘complete’ and ‘applicable’ range fits of the experimental σ–? data. At all strain rates, in the case of the complete range fit, the Ludwigson equation followed the stress–strain data most closely at 300 K, while in the temperature range 523–773 K, the flow behaviour was described equally well by both the Ludwigson and Voce equations. In the temperature range 823–1023 K, the Voce equation described the flow behaviour most accurately in the case of the complete range fit of σ–? data at all strain rates. The analysis of σ–? data employing the Ludwigson equation in the applicable range fit covering low and intermediate strains, and the Hollomon equation at high strains provided close simulation of the observed flow behaviour in the temperature range 823–1023 K. At high temperatures of 1073 and 1123 K, the Ludwigson equation reduces to the Hollomon equation. The variations in different flow parameters of the Ludwigson and Voce equations with temperature and strain rate exhibited anomalous behaviour at intermediate temperatures because of dynamic strain aging.     

Corrosion resistance of Ti-6246 for high power aeroengine compressor discs and blades

Abstract

The corrosion resistance between 723 and 1123 K of Ti-6246 has been investigated. For temperatures between 723 and 823 K, the maximum weight gain in air was below the measurable range. For the temperature range 873–1123 K, there was substantial weight gain with reaction time with a maximum weight gain of 180×10^-4 g cm^-2 being obtained after 150 h at 1123 K. Weight gain for the vacuum tests remained constant over all temperatures and reaction times with a maximum observed increase of 3×10^-4 g cm^-2. There was evidence in favour of parabolic rather than linear increases in weight gain with time. The parabolic and linear rate constants increased with temperature and the activation energy associated with parabolic oxidation was estimated as 216 kJ mol^-1. The life of Ti-6246 in argon at 773 K was found at certain stresses to be almost twice that obtained in air. This difference could not be explained by the loss of load bearing cross-sectional area following oxidation.     

Wear behaviour of Fe3 Al intermetallic particle reinforced PM based iron metal matrix composites

Abstract

The wear behaviour of unreinforced and reinforced PM based iron metal matrix composite, the latter containing 10 and 20 vol.-% nano sized Fe₃Al intermetallic particles, was studied as a function of sliding distance under two different loads and dry lubricated conditions. The intermetallic Fe₃Al nanoparticles were prepared by mechanical alloying and used as particle reinforcement with 10 and 20 vol.-% in the matrix. The processing of the composites included mixing and cold compaction followed by sintering at 1120°C. The influence of Fe₃Al additions on the dry sliding wear behaviour was studied at loads 20 and 40 N over sliding distances 2160, 3240, 4320 and 6480 m. The study showed that the composite exhibited a lower wear rate than that of the unreinforced matrix and the wear rate was influenced by the volume percentage of Fe₃Al particles. It is understood that iron aluminide reinforcement has a beneficial effect on the wear properties. Delamination and microcutting were the chief mechanisms of wear for the composites.     

New approach for prediction of roll force in rod rolling

Abstract

An approximate model is presented in which the equation for computing roll force in an oval-round (or round-oval) pass rolling sequence has been formulated with a new approach. The fundamental idea considered is to introduce the concept of a weak plane strain condition which gives a two-dimensional approximation of the three-dimensional deformation problem in rod or bar rolling. The generality and robustness of the model have been examined by conducting a two-pass low speed bar rolling experiment and a four-pass continuous high speed rod rolling test with various rolling temperatures, roll gaps (pass height), rolling speeds, and steel grades. The predicted roll forces were in good agreement with those experimentally measured, although the prediction was less good when the roll gap (pass height) varied. The proposed model was very fruitful in solving the three-dimensional deformation problem in rod or bar rolling.     

Similar and dissimilar RSW of low carbon and austenitic stainless steels: effect of weld microstructure and hardness profile on failure mode

Abstract

In this paper, the failure behaviour of similar and dissimilar resistance spot welded joints of low carbon and austenitic stainless steel sheets was studied under tensile shear test with attention focused on the failure mode. Results showed that the microstructure of the fusion zone and the hardness distribution across the weld have a profound effect on the failure behaviour. Similar spot welds of stainless steel sheets exhibit the highest tendency to fail in interfacial failure mode, compared to low carbon steel similar spot welds and dissimilar low carbon and stainless steel spot welds. This behaviour is explained by the consideration of pullout failure location and hardness profile characteristics of each joint. It was shown that the failure mode transition is controlled by the hardness ratio of the fusion zone and the pullout failure location. In the case of dissimilar resistance spot welding, the hardness of the fusion zone which is governed by the dilution between two base metals, and the fusion zone size of the low carbon steel side are the dominant factors determining the failure mode of the joint.     

Continuous elimination of Al2O3 particles in molten aluminium using electromagnetic force

Abstract

A new method for continuous elimination of inclusions by using electromagnetic force was designed in this study. The principle is that as the electromagnetic force induced in metal scarcely acts on inclusions owing to their low electric conductivity; they are moved in the direction opposite electromagnetic force and can be separated from the melt. To do this, numerical analysis was conducted by employing the principle of electromagnetic braking. Numerical results agreed well with the experimental ones. Using the continuous electromagnetic separation system designed in this study, it was determined that Al₂O₃ particles whose size was larger than ~ 14 μm immersed in flowing aluminium melt could be removed under the electromagnetic conditions (electric current density 7.96 × 10⁵ A m^-2, magnetic flux density 0.35 T) when the flow velocity was ~ 150 mm s^-1.     

Wear behaviour of 85Al–10La–5Ni alloy prepared by powder metallurgy

Abstract

The dry wear behaviour of 85Al–10La–5Ni (at.-%) alloy hot pressed has been studied. The result shows that 85Al–10La–5Ni alloy possessed excellent wear resistance. The wear resistance of the alloy pressed at 773 K is three times as high as that of the A355 aluminium alloy. The fine high hardness intermetallic compounds contribute to the wear resistance of the alloy.