This chapter focuses on two kinds of environmental fracture, stress corrosion cracking (SCC) and hydrogen embrittlement, and discusses the role in such failures of a number of metallurgical variables. These include chemical composition; microstructural components such as precipitate type and structure, and grain size and shape; crystallographic texture; heat treatment and its effect on the foregoing variables; and processing, particularly the thermomechanical treatments (TMT), which are attracting increased attention for property optimization. These variables are expected to be of great importance in the development of new engineering materials to meet demanding service conditions.

The Role of Metallurgical Variables in Hydrogen-Assisted Environmental Fracture

Hydrogen surface effects in ferritic stainless steels

Effects of dissolution on plastic deformation and cracking of metals

The corrosion behavior of two aluminum alloys Al 6061 T6 and Al 2024 T3 was investigated in a low carbon fuel consisting of concentrated aqueous solutions of ammonium nitrate and urea (ANU). Weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques were applied to study the alloys corrosion behavior. Results obtained showed that a corrosion resistance passive film was formed on the surface of both aluminum alloys in solutions of pure ANU and ANU containing up to 1% NaCl. No flawed regions were found on the surface of either alloy after immersion in both solutions for 1500 h. However, immersion of the metals into pure 1% NaCl solution resulted in corroded regions immediately after immersion. The results received from weight loss, polarization, and impedance measurements are in excellent agreement. The high corrosion resistance of both Al alloys in the ANU solution containing up to 1 wt% NaCl support a safe usage of these materials for construction of storage containers and piping of these solutions.

H. H. Uhlig

Papers

Differentiating Stress Corrosion Cracking from Hydrogen Cracking of Ferritic 18-8 Stainless Steels