An investigation was carried out on variation of oxidation behavior to be seen when the alloy compositions shift along a single tie line. The specimens were prepared from the alloys whose composition lay on the tie line of Rene-95 at 760°C or its extension. Oxidation was performed in oxygen at 1000, 1100 and 1200°C. A parabolic law was held for every alloy at 1200°C. A logarithmic law was held for every alloy but one at 1000°C. At 1100°C the behavior was parabolic for the alloys near to the γ-region and logarithmic for the alloys in or near to the γ'-region. The behavior of the intermediate region was near-parabolic in the first half, while it was near-logarithmic in the second. The reactivity generally decreased monotonously towards the γ'-region at all temperatures. The reactivity was, however, higher than the general trend for the alloys which were composed of two phases at the oxidation temperature as well as for the alloys within the γ'-phase region when the oxidation temperature was 1200°C.
Corrosion behavior of TiN film coated by an arc ion plating on type 304 stainless steel in demineralized water at 286°C was studied using the circulating type experimental loop. Exposure tests were carried out under three different dissolved O2 concentratins of less than 10μg/l, 150μg/l and 1, 000μg/l, respectively. Corroded surface was observed by EPMA, XRD and XPS. On the exposed specimen surface, the corrosion film composed of TiO2 was formed, which increased the weight of specimen after exposure. This weight gain varied largely by dissolved O2 concentration and it increased by several times with an increase of dissolved O2 concentration. It was assumed from the relationship between dissolved O2 concentration and the corrosion rate of TiN that TiN could react with both H2O and O2, although the dissolved O2 became a dominant factor for corrosion increase at concentrations over several 10μgs/l.
All specimens as rusted, phosphated, and chemically treated with a 0.1M Na2MoO4-H3PO4 solution after wire-brush scratching were found to have the same BET type of adsorption isotherm by N2 adsorption. Their pore size distribution peaked at about 100nm radius, and then decreased abruptly until 500nm and thereafter slowly until 1500nm. The chemically treated wire-brush scratched rusted steel was small in specific surface area and in all pore volumes as compared with other specimens probably due to the formation of conversion coatings at exposed bare areas which have existed on the rusted surface or been caused by wire-brush scratching. It seems that sludges were adsorbed at these bare areas and caused pores to be partly clogged.
A fretting corrosion testing apparatus was constructed in order to simulate the corrosion damages of biomedical materials in human body. By means of this testing apparatus and electrochemical approach, the fretting corrosion test of 316L stainless steel was performed to establish the in vitro test condition, and to obtain the useful information for the improvement of biomedical stainless steels. In continuous fretting corrosion test of 316L stainless steel, it was found that fretting enhanced crevice corrosion did not occur even when specimen was potential-controlled above 0mV (SCE) where growth of crevice corrosion is more susceptible. However, during the intermittent fretting corrosion test, growth of crevice corrosion occurred remarkably at the resting stage, and the anodic current corresponding to the release of metal ions, was one order of magnitude higher than that at the fretting stage. Therefore, it was recommended that intermittent fretting corrosion test is more significant for the evaluation of stainless steels. The application of high Mo modified stainless steel is very effective to suppress such crevice corrosion at resting stage.
Micromachines are invisibly small and yet composed of many complicated elements. Among many studies of micromachines, mechanisms and actuators of μm in size are reviewed with their fabrication processes which are compatible with IC technology. The processes, called micromachining, can solve problems which have prohibited conventional mechanical machining from making such small machines. Micromachines will be equipped with sensors, actuators, and electronics. Although sensors and electronics are well developed, the study of microactuators have just been started. Recent topics in microactuators and their applications in surface science are discussed.