LASER SURFACE ALLOYING OF A MILD STEEL FOR CORROSION RESISTANCE IMPROVEMENT

Surface alloys were produced by laser melting of different predeposits into the outer part of a mild steel substrate. Three types of coatings were used : electroless nickel (containing phosphorous), electroless nickel in which chromium carbide particles were introduced during deposition and duplex coatings made of, first, a nickel layer (electroless or electrodeposited) and then, a chromium layer. The surface alloying treatments were performed using a cw high power CO2 laser and the multiple track melting technique with 60 % overlap between each track. A single laser scan was used. The obtained surface alloys show excellent adherence without porosity or cracking. A detailed microstructural investigation revealed a fine dendritic microstructure. Phosphorous, when present, is segregated in the interdendritic areas. The corrosion resistance of the surface alloys was tested by electrochemical techniques in various neutral or acidified saline media deaerated or naturally aerated. With the first type of predeposit, surface alloys exhibit a corrosion resistance similar to that of electroless nickel but with a much higher adherence of the coating to the substrate. With the second type of predeposit, the increase in corrosion resistance is limited due to the low chromium concentration obtained in solid solution. On the contrary with the third type of predeposits (duplex layers), surface alloys exhibit a high corrosion resistance especially when electrolytic nickel coating was used

Degradation des revetements sacrificiels appliques sur acier

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : AR 16137 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueMinistere de l'Enseignement Superieur et de la Recherche, 75 - Paris (France)FRFranc

Loss-of-vacuum, loss-of-coolant, and loss-of-flow accident analysis for NET ITER

Analyses are presented οη hypothetical accidents in NET/ITER involving: -air ingress in the graphite-coated plasma chamber through a breach in the vacuum vessel (LOVA); -loss-of-coolant inside the vacuum vessel with water ingress in the plasma chamber (inside LOCA); -loss-of-coolant outside the vacuum vessel (outside LOCA); -loss-of-power with the worst case conditions of absence of any cooling by natural convection (total LOCA) , and with natural convection flow (total LOFA). Ιn this paper the modeling of these accidents and important results are shown

Loss-of-vacuum, loss-of-coolant, and loss-of-flow accident analysis for NET ITER

Analyses are presented οη hypothetical accidents in NET/ITER involving: -air ingress in the graphite-coated plasma chamber through a breach in the vacuum vessel (LOVA); -loss-of-coolant inside the vacuum vessel with water ingress in the plasma chamber (inside LOCA); -loss-of-coolant outside the vacuum vessel (outside LOCA); -loss-of-power with the worst case conditions of absence of any cooling by natural convection (total LOCA) , and with natural convection flow (total LOFA). Ιn this paper the modeling of these accidents and important results are shown