Evaluation of AFC 77Martensitic Stainless Steel for Airframe Structural Applications.

摘要

The fabrication and properties of two high-strength stainless martensitic steel forgings are described. A high level of fracture toughness was achieved in the AFC 77forging at a tensile strength level of 235ksi. Stress corrosion resistance,however,was similar to that of competitive steels. The fracture toughness,stress corrosion,and fatigue properties developed in the AFC 77B forging at a tensile strength of 260ksi were similar to those of currently used steels. Cracking problems were experienced with both forgings during heat treatment. The stress corrosion resistance of AFC 77was no higher than that of competitive steels. The target tensile strength of 275ksi was not achieved in the AFC 77B landing gear forging. A lower tensile strength would appear to be more appropriate for this alloy in heavy section form. The fracture toughness,stress corrosion,and notch fatigue properties were very similar to those of medium alloy steels. Although both AFC 77and AFC 77B are stainless types of steel,it is considered that the low stress corrosion resistance would necessitate plating and painting to prevent the ingress of moisture. (Modified author abstract)