The solid to liquid phase transformation of LiOH has been proposed as an ideal candidate thermal energy storage media for a Rankine Cycle powered electrical generation unit envisioned in Space Station based solar dynamic systems. Due to the corrosive nature of molten hydroxides, long term containment of LiOH is of concern. Pure nickel is thought to be a suitably resistant material, and a program has been instituted to measure the effects of prolonged exposure of liquid and gaseous LiOH on the mechanical properties of pure nickel alloys. Results to date indicate that negligible weight and thickness changes occurred in Ni alloys exposed to LiOH for as long as 2500 hr at 775 K, and essentially no difference in 77–900 K tensile properties could be detected between LiOH exposed and vacuum annealed Ni specimens. Although there was little sign of outward damage, microstructural examination revealed that all hydroxide contaminated tensile test specimens had surface connected intergranular cracks along the gage lengths. Two other potential problems, which have strong implications with respect to a LiOH/Ni energy storage system, were also noted during the corrosion experiments. In particular stress corrosion cracking of weld joints in pressurized vessels and permeation of hydrogen through nickel, which leads to the loss of LiOH, were observed.

The requirements for increasing operating temperatures in gas turbines and fuel fired energy systems is linked to the use of protective coatings able to improve oxidation and corrosion resistance of structural materials. MCrA1Y-type overlay coatings have been especially designed to protect airfoils and other hot gas component superalloys against hot corrosion induced by molten salts in lower grade fuel and aggressive environments. However, aluminide coatings modified by additional elements have gained renewed interest because they offer an economical alternative to physical vapor deposition or plasma spray coating processes used to apply the MCrA1Y’s. Of the possible modifiers, chromium and platinum are the most prevalent elements used. Although they have been in field service for a number of years, there are some controversies on the reasons for their beneficial effects. The present literature on the corrosion behavior of chromium and platinum modified coatings is reviewed and updated in light of the structural dependence of corrosion resistance for both coating types. The formation mechanisms and the related structures of chromium aluminides are presented together with results of recent investigations aimed at defining the structural variations of platinum aluminide coatings which depend on the deposition parameters, that is, the platinum prealuminizing treatment and the subsequent aluminizing process.

Erosive particle impacts can result in the high strain rate deposition of an appreciable amount of energy into the deformed volume of the target material. This energy likely causes local heating; softening or even melting has been observed in many materials. Hardening caused by the high-strain-rate deformation has also been reported for strain-hardenable materials. The effect of individual impacts on the surface of selected aluminum alloys was determined both analytically using theoretical considerations and experimentally using 343 Μm diameter tungsten carbide balls impacting at about 30 m/s and 30 deg incidence angle. After impact a mechanical properties microprobe was used to measure the hardness of both the crater bottom and material just below the original surface. Strain hardening, but no evidence of softening, was observed for two aluminum alloys.

Fatigue life tests in pressurized water reactor (PWR) environments were performed on smooth and sharply notched specimens of ASME SA-106-B piping steel at cyclic frequencies of 1.0 Hz, 0.1 Hz, and 0.017 Hz. On the basis of these tests, it was concluded that no effect of cyclic frequency existed for smooth specimens whereas a frequency of 0.017 Hz proved to have the most detrimental effect on the cyclic life of the notched specimens. However, a reduction in fatigue strength in the low cycle fatigue regime and a fatigue strength enhancement in the high cycle regime was observed in both 288° C (550° F) air environment tests and PWR environment tests. This is believed to be due to dynamic strain aging processes. As a result, the current ASME Section III design curve for carbon steels is nonconservative in its positioning, which may decrease the presumed safety factor against fatigue failures in carbon steel piping components having structural discontinuities.

High strength heat resistant alloys owe their high temperature corrosion resistance to the scales that form under the environmental conditions to which they are exposed. Because of the trend to higher temperatures, six alloys—INCONEL alloy 617, INCO alloy HX, NIMONIC alloy 86, INCOLOY alloy MA 956, and Haynes alloys 188 and 214—were selected for study in three environments: air plus 5% water vapor, oxygen plus 4% SO2, and JP-5 fuel in a burner rig. The alloys were evaluated by conducting mass change analyses, and the chemical nature of the scales was determined by x-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX). In this paper the mass changes produced by exposure to these environments are reported and the results are correlated with the chemical nature of the scales formed during testing. The results indicate that alloy MA 956 performed exceptionally well in all three environments. Its superior performance is attributed to the alumina scale adherence, which is promoted by an yttria dispersoid that is distributed evenly by the mechanical alloying process.

Cleaning of coals by physical and chemical methods and micronizing is considered to improve the combustion efficiency and increase the heating value of coal. From the component materials viewpoint, the environment established by combustion of cleaned coal and its interactions with materials are of interest. For this purpose, several modes of materials degradation such as deposition/fouling, corrosion, and erosion relevant to coal fired systems are discussed, and the influences of physical and chemical properties of coal and mineral matter on the degradation mechanisms are presented. Combustion characteristics of cleaned coals are examined, and their effects on fly ash formation, deposition processes, alkali and sulfur attack of materials, and erosive wear of materials are analyzed.

Among the light metal alloys, magnesium is the lightest structural material except for beryllium, and yet magnesium alloys have not seen extensive use because of their poor strength and corrosion resistance. Rapid solidification technology offers a possible solution to these problems. A number of Mg-Al-Zn alloys containing rare earth (RE) elements (e.g. Ce, Pr, Y, and Nd) have been investigated using rapid solidification processing for possible structural applications. The processing consists of planar flow or jet casting into ribbons, pulverization of ribbon to powder, and consolidation of powder into bulk shapes. The mechanical properties of some of these alloys show attractive combinations of strength (UTS-513 MPa), ductility (tensile elongation-5%) and corrosion resistance [corrosion rate of 11 milligrams per square decimeter per day (mdd) in 3% NaCl solution]. The microstructures of these alloys are correlated with their mechanical properties. The rapidly solidified Mg-Al-Zn-RE alloys show great potential for applications in automotive and aerospace industries.

A series of tests have been conducted in the National Research Universal (NRU) reactor, Chalk River, Canada, to investigate the behavior of full-length 32-rod PWR fuel bundles during a simulated large-break loss of coolant accident (LOCA). In one of these tests (MT-3), 12 central rods were prepressurized in order to evaluate the ballooning and rupture of cladding in the Zircaloy high-α/α + Β temperature region. All 12 rods ruptured after experiencing < 90 pct diametral strain, but there was no suggestion of coplanar blockage.