Selective corrosion in a hot hydrochloric acid service was noted in a narrow band of the heat affected zone of a commercially fabricated zirconium weldment. Little attack was present on the weld proper or the parent stock. The selective attack has been found to be intergranular in nature and associated with the presence of a precipitated phase in the grain boundaries. The particular precipitated phase required for this attack has been duplicated in bulk samples by specific heat treatment, as well as in experimental weldments. Two methods of prevention of this localized attack near welds have been evaluated; namely: (1) Use of high purity zirconium, and (2) heating of commercially pure zirconium weldment at 1800 F followed by a water quench. Possible mechanisms for the microstructural changes and for the corrosion attack are discussed. 6.3.20, 3.2.2, 4.3.2, 3.7.3

Thermal-expansion, stress-temperature, and thermal-shock tests were conducted on glassed low-alloy and plain-carbon steels. The addition of alloying elements increases the hardenability and strength of the steels but lowers the austenite-to-ferrite transformation temperature, thus decreasing the residual compressive stress in the glass coating and therefore its resistance to thermal shock. It is shown that DI, the calculated hardenability index, may be correlated with certain physical properties of the glass-steel composites.

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