On low carbon steel specimens vacuum carburized at temperatures in the range from 1193 to 1313 K in a methane atmosphere at pressures ranging from 13 to 80kPa, carbon content profiles within the specimens were determined from a succession of grindings and carbon analyses with a vaccum type emission spectrometer.The total amount of carbon which entered each specimen through the surface during a carburizing period was graphically calculated from the profile, and the rate of carburizing was evaluated from the amount of carbon. It was found that the rate of vacuum carburizing with methane had the temperature dependence several times as strong as that of gas carburizing. A mathematical model for calculation of such carbon content profiles is presented. The model in which the variation of carbon diffusion coefficient in steel with carbon content was taken into consideration predicted accurately the surface carbon content and case depth of vacuum carburized steel.
Residual stress produced in titanium nitride films deposited onto substrates of high speed steel, SKH51, was studied by using sin 2 c method as a function of process parameters: deposition temperature, deposition time, electron beam current, substrate bias voltage, distance from an evaporation source to a substrate, tilt angle of a substrate axis, total gas pressure, and gas mixture ratioMeasurements showed that compressive stress occurred in the films except one deposited without any applied bias voltage to a substrate. Applying a little bias voltage to a substrate brought about a rapid increase in the compressive stress. Higher deposition temperature and lower deposition rate reduced the compressive stress. A decrease in total gas pressure increased the compressive stress. These results suggest that kinetic energy of incident ions on a substrate affects the generation of the compressive stress. In plane lattice parameter increased with an increase in compressive stress; this variation was in good agreement with the distance calculated on the basis of the Poisson ratio effect. Hardness of the films increased with an increase in the compressive stress. Grain size of the films was determined by the method based on``Williamson Hall plot'' which can exclude the contribution of micro strain from line broadening of X ray diffraction. Hall Petch relationship is established between the grain size and the hardness. It seems that mobility of adatoms is closely related to the magnitude of the residual compressive stress.
We have fabricated carbon nanotubes (CNTs) using a catalyzed growth technique that we call the carbon transmission method (CTM). We could control independently functions for carbon source gas supply and CNT growth by using a foil barrier (Ag) penetrated by pure Fe fibers. CNTs grew on one end of the Fe fibers, formed from diffused carbon that originates in carbon source gas at the other end of the fibers. Long CNTs with length over 100 µm were obtained on the end of the Fe fibers in the carbon transmitted side.
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