Embrittlement of High Strength AISI 4340 Steel in Boiling NaCl Solution^*

The resistance of high strength AISI 4340 steel tubing, quenched in oil and tempered at 425 F (218 C), to corrosive media has been investigated. The exterior surface of the specimen was exposed to boiling NaCl, the interior cavity was evacuated and the specimen was subjected to a tensile stress. Specimens failed, with little evidence that cracking was developing, after several hours’ exposure and after hydrogen had penetrated through the specimen wall. Appearance of the initial fracture and its mode of development indicate it originated within the specimen wall. The data indicate that failure resulted from hydrogen embrittlement