The susceptibility of steels to catastrophic failure by metal dusting is known to depend upon the activity of the carburising environment, alloy chromium content, grain size, surface condition and temperature. This paper presents results of first tests investigating the influence of gas pressure on metal dusting of 9 – 20% Cr containing steels, by increasing the test gas pressure to approximately five bar over atmospheric pressure. Cross‐sectional micrographs show attack morphologies such as intergranular and internal carbide formation, as well as the classic uniform and pitting types of attack.

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Dedicated to Professor Dr. H. J. Grabke on the occasion of his 60th birthdayThe ability of alloys to resist corrosion during exposure to high temperature process atmospheres is one of the primary factors governing their selection in the manufacture of components such as heat exchangers in coal conversion plant. In particular, sulphidation attack in the low oxygen-containing environments often encountered in such plant can pose significant problems.Many laboratory studies have been carried out over the years in gases simulating those found in coal gasifiers but these experiments have almost always utilised equilibrated gas mixtures in which the activities of the principal reactants, S, 0 and C were known and controlled. In many industrial situations, however, the combustion gases are quenched from very high temperatures, e.g. 1200-1400 "C before coming in contact with the much cooler heat exchanger tube surfaces and therefore chemical equilibration between the gaseous constituents does not have time to occur. This paper presents results from a study concerned with the corrosion behaviour of candidate heat exchanger alloys exposed to a CO-rich, non-equilibrated gas mixture of the type found in a dryfeed entrained slagging gasifier. Data on three selected alloys, i. e. HR 3C (a chromia-former), MA 956 (an alumina-former ) and HR 160 (a silica-former) exposed at 600°C are reported. The kinetics and mechanisms of corrosive degradation are described for test durations of up to 2000 hours. Significant differences in corrosion rate and in the depths of metal loss exhibited by these alloys were observed. Alloy HR 160, containing approximately 2.75% Si, exhibited the best corrosion resistance.

Shallow boron-doped junctions in silicon have been investigated by means of secondary ion mass spectrometry, scanning electron microscopy, transmission electron microscopy, spreading resistance profiling, and four-point probe techniques. The junctions were formed by implanting BFt ions into n-type Si at the dose range of 1-5 X 10 15 ions/cm 2 , through a thin (25-nm) screen layer of silicon dioxide. We have emphasized the higher dose range (3-5 X 10 15 ions/cm 2 ) as it is more relevant to processes in the current level of device integration. The use ofBF 2 + species and the screen oxide layer is necessary in order to form junctions whose depths Xj .,;;0.4 pm, when conventional annealing techniques are employed. We have also examined junctions that were activated in a rapid thermal annealing system that utilizes an incoherent light source. One of the main objectives of this study is to compare conventional and rapid thermal annealing techniques. We thus evaluate the results obtained by these two methods of annealing for both the junction depth Xj and the sheet resistivity Rs' Other relevant variables such as a low-temperature (77-K) implantation, surface amorphization by Si implantation, and preactivation annealing have also been examined and their effects are discussed. Based on the results of the present study, a mechanism for boron activation in silicon is discussed.