Hydro-Québec

About: Hydro-Québec is a government organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Electric power system & Dielectric. The organization has 2596 authors who have published 4433 publications receiving 100878 citations.

Environmental Variables in the Low Temperature Stress Corrosion Cracking of Inconel 600

Abstract: The low temperature stress corrosion cracking of sensitized Inconel 600 has been examined using aerated 1.3% boric acid solutions with small additions of sodium thiosulfate. Cracking is observed for thiosulfate concentrations above 10−6 M. The rate of cracking increases with temperature to at least 80 C. Concentrated solutions with potential control give crack velocities up to about 0.4 μm/s at 22 C. Provided that cracks are initiated by slow straining, they continue to propagate at very low apparent stress intensities. Lithium hydroxide additions inhibit SCC by producing borate anions; the rate of borate to thiosulfate ion concentration is an important factor in determining immunity to SCC.

Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

Abstract: In the as-quenched state, 13%Cr–4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

Influence of rain on switching impulse sparkover voltage of large-electrode air gaps

Abstract: The paper deals with a laboratory investigation into the influence of rain on the switching impulse sparkover characteristics of large-sphere and toroid plane air gaps. Tests were also carried out on coneterminated rod-plane gaps for reference purposes. The factors investigated include the high voltage electrode geometry, nature of the surface, rain intensity as well as the impulse form and polarity. Attention is also paid to the influence of rain on the statistical dispersion of the sparkover voltage and on the nature of the cumulative probability curve. A general correlation, valid for a wide variety of electrodes, has been established between the mean spark-over voltage gradient for positive switching impulses under dry conditions, and the corresponding influence of rain on the breakdown voltage.