CHARACTERIZATION OF STRESS CORROSION CRACKING (SCC) IN ULTRA-HIGH
STRENGTH STAINLESS STEEL
Greger L. Pioszak
Advisor: Dr. Richard P. Gangloff
Department of Materials Science and Engineering
University of Virginia, Charlottesville, VA 22904, USA
Abstract
Ultra-high strength precipitation hardened martensitic stainless steels (UHSSS) are increasingly
used in aerospace applications as a replacement for ultra-high strength low alloy steels since
stainless character eliminates the need to plate high strength components with toxic cadmium for
corrosion resistance. However, modern UHSSS alloys remain susceptible to severe intergranular
stress corrosion cracking (IGSCC) and transgranular stress corrosion cracking (TGSCC) when
stressed in chloride containing environments. The primary goal of this research is to characterize
the stress corrosion crack growth kinetics and fracture morphology for hydrogen environment
assisted cracking (HEAC) in UHSSS. Subcritical crack growth experiments have been optimized
to provide high resolution measurements of SCC crack growth in Custom®465 and
Ferrium®PH48S™ at constant applied potential in aqueous NaCl solution. Results establish that
a combination of composition and heat treatment changes applied to Ferrium®PH48S™ have
increased the SCC resistance and changed the dominant fracture mechanism from intergranular
to transgranular, compared to Custom®465. Metallurgical variables are hypothesized to control
the concurrent increase in SCC resistance and change in fracture mechanism and
Ferrium®PH48S™.
Pioszak
1