High Temperature Corrosion-Fatigue Test Method for Exhaust Valve Alloys

A rotating beam fatigue test method was developed to determine the high-temperature corrosion-fatigue properties of valve alloys under cyclic stress in a simulated engine operating environment. The test results showed that microstructural modification of an alloy through heat treatment can significantly improve corrosion-fatigue properties. For test development purposes, Nimonic 80A was selected for testing and a mixture of lead compounds was used as the corrosive environment. This is a typical combination of alloy and environment found in heavy-duty spark-ignited engines. This test method may also be applicable to other corrosion-fatigue problems such as sulfidation in diesel exhaust valves.