STRESS-CORROSION CRACKING OF TITANIUM AND TI-AL ALLOYS IN METHANOL- IODINE SOLUTIONS
Abstract
Studies of the mechanical behavior of unalloyed titanium in methanol- halogen solutions have led to the suggestion that stress-corrosion cracking (SCC) in these environments occurs by localized anodic dissolution at the crack tip. The validity and generality of this model for SCC has been examined by means of comparative studies of the corrosion characteristics and susceptibility to SCC of pure titanium and Ti-Al binary alloys in methanol-iodine solutions. Evidence is presented which indicates that two distinct SCC mechanisms may be operative, namely (i) stress accelerated intergranular corrosion involving dissolution of metal at a crack tip, and (ii) a transgranular cracking process which has the characteristics of mechanical failure. The characteristics of SCC failures of pure titanium and the Ti-2.1 w/o Al alloy appear to be consistent with the dissolution model. In the higher alloys (>5 w/o Al), however, dissolution appears to be responsible only for the crack initiation stage, propagation involving transgranular cracking. Stress-corrosion failure in the higher alloys may therefore be prevented by inhibiting the initiation process via cathodic polarization or the introduction of passivators (i.e. water) into the testing environment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1968
- Accession Number
- AD0671680
Entities
People
- A. J. Sedriks
- J. A. S. Green
- P. W. Slattery
Organizations
- Martin Marietta