Laminated plate composites were prepared by hot roll bonding together plates of 18Ni(280) maraging steel and sheets of Armco iron. Composite welds of the same geometry were also prepared by successively depositing weld layers of these two materials. Plane strain stress corrosion tests of these two types of composites in aerated 3.5% NaCl solutions showed that stress corrosion crack propagation was stopped at stress intensities well above the KISCC values of the corresponding homogeneous maraging steel base plate and maraging steel weld metal. The results demonstrate that it is possible to retard stress corrosion crack propagation significantly in both base plate and weld structures by the use of a composite approach.
Laminar composites were prepared of outer layers of 18Ni (200) maraging steel with various inner layer materials. The composites showed reasonable fabricability in both hot and cold working operations. The materials were weldable, and the composite structure could be continued through the weld zone using conventional welding techniques. Yield strengths on the order of 200 ksi were obtained along with excellent crack stopping ability in impact, fracture toughness, stress-corrosion, and fatigue loading. In general, good combinations of fabricability and crack stopping ability can be achieved through the use of soft, relatively thick internal layers that are well bonded to the outer layers.
The creep rupture behavior, and the effects of elevated temperature exposure in air and hydrogen on the subsequent room temperature properties of a 12 percent Ni-5 percent Cr-3 percent Mo maraging steel are described. Tests have been made on several heats of plate and on gas tungsten-arc, gas metal-arc, and electroslag welds. On the basis of the results obtained, maraging steels offer promise as high-strength steels for service at elevated temperatures.
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