METALLURGICAL EVALUATION OF FAILED AIRCRAFT STAINLESS STEEL EXHAUST SYSTEM COMPONENTS
Abstract
A total of twelve samples from small aircraft exhaust systems were investigated metallurgically. Three of the samples, referred to as baseline, were from new, unused systems. These were examined metallographically for general microstructural characteristics and chemically analyzed. The other samples were from systems which had failed while in flight operation. These samples were examined metallographically and analyzed chemically to determine the cause(s) of failure. The samples were representative of a number of designs and different types of failures which have been encountered. Practically all the materials were AISI Type 321, a titanium-stabilized austenitic stainless steel. Examination of the baseline samples showed microstructures of the base metal, weld and weld heat-affected zone to be normal. Four samples failed because of excessive oxidation or high temperature corrosion due apparently to uneven flow of gases, resulting in local overheating, carburization, and probably more rapid attack by the products of combustion, especially lead compounds. Four other samples from mufflers of similar design and one sample of a different design showed fatigue cracks. The failures were attributed to excessive vibrational and/or thermal stresses in the presence of abrupt changes in section size and likely locations for crack initiation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1965
- Accession Number
- AD0614913
Entities
People
- T. H. Mccunn