Submicron and Nanoscale Structure of an Ultra-High Strength Precipitation Hardenable Stainless Steel

摘要

Carpenter Custom 475~(TM) is an ultra-high strength precipitation-hardenable stainless steel capable of tensile strengths in excess of 280-ksi. The material possesses an iron-nickel lath martensite matrix and it has been previously assumed that a number of submicron scale precipitates were involved in the age-hardening mechanism. A series of investigations were carried out to fully characterize both the structure of the grade and its response to variations in thermo-mechanical processing. The material was determined to reach full solution at approximately 1650 deg F, with no degradation of strength with solution temperatures up to 1800 deg F. Peak strength, as determined by hardness testing, was observed to occur at 1000 deg F for a four hour one-step aging treatment, although hardening was found to occur at temperatures as low as 650 deg F. Preliminary TEM and STEM characterization of multiple precipitates was performed along with a determination of the amount and distribution of retained and reverted austenite contents.