Field experience and preliminary laboratory data have shown that the techniques of thermoelectric sorting could become a valuable tool in the assessment of precipitation-hardening stainless steels. The Phase I investigation involved heat-treating a variety of carefully controlled specimens and correlating their thermoelectric characteristics with heat-treating variables.The thermoelectric characteristics of five different types of precipitation-hardening steels were found to be strongly correlated with both Rockwell hardness and with time and temperature of aging. A similar situation was discovered to exist for the nickel-based, heat-resistant alloy, Inconel 718. The results of these tests along with several instrument improvements, particularly for small specimens, suggest the feasibility of developing new thermoelectric instruments for the assessment and study of a wide variety of precipitation-hardening alloys. Of particular interest are their use for testing heat-affected zones around welds and studying damage or reduced service life in components subjected to high service temperatures. Further, a specialized instrument can be built for non-destructive examination of a wide variety of miniature specimens ranging from research materials to precious metals to samples used in forensic investigations.Potential Commercial Application:Primary uses are in the assessment of the condition of both precipitation-hardening stainless steels and heat-resistant, nickel-based alloys commonly used in the aerospace industry. Other applications include precious metal control, materials research, and forensic investigation.STATUS: Project Proceded to Phase II
