An electrochemical model for hot-salt stress-corrosion of titanium alloys

Garfinkle, M.

doi:10.1007/bf02666196

Cited by 19 publications

(16 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This would account for the chlorine 535 identification in the blue spot layer and is consistent with previous studies that state chloride ions would be expected to extend down the crack [33]. It is hence believed that the blue spot layer is formed via reaction 3 and is associated with the deposition and consequent rupture of the TiO 2 reaction product near the mouth of the crack.…”

supporting

confidence: 88%

“…The deposited TiO 2 splits and condenses onto the crack walls near the mouth, allowing further hydrolysis of titanium chlorides and a looping process between reactions 2 and 3 to proceed. The proposed mechanism considers water, via gaseous HCl, to be the source of hydrogen in this HSSCC mechanism, a hypothesis which is supported by many from the 1960s and 70s [6,33]. Chloride is therefore the means by which 485 hydrogen from water molecules is transported into the crack tip.…”

mentioning

confidence: 97%

“…Most studies do not explicitly state where the water comes from, though it is commonly considered either to be from moisture in the atmosphere, or fluid inclusions in the salt [6], or adsorbed 400 onto the titanium surface [32]. Only small quantities are required [33]. Although no direct evidence was found from our results, traces of sodium titanate have been determined from X-ray diffraction experiments in previous studies [5] and production of Na 2 TiO 3 (via reaction 1) has been found to be thermodynamically favourable [34].…”

mentioning

confidence: 99%

“…The deduction is that nascent hydrogen is adsorbed onto the exposed titanium at the base of the channel from where it diffuses into the bulk metal. It is widely accepted that the hydrogen concentrates just ahead of the channel, in a region of high hydrostatic stress when under load [39, 40,33,41]. Hydrogen would be expected, for instance, to concentrate at dislocation cores 440 and other plasticity related defects that increase the volume of interstitial sites.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Environmentally assisted fatigue crack nucleation in Ti–6Al–2Sn–4Zr–6Mo

et al. 2015

View full text Add to dashboard Cite

An unexplained feature was observed at the fatigue crack origin of a number of α/β titanium specimens tested at 450• C in the low cycle fatigue regime. The origin was discoloured blue but this was not a result of temper colouration; this feature sometimes resulted in large reductions in fatigue lives. A number of specimens were examined to determine the cause and formation mechanism of these "blue spots." This feature was associated with elevated oxygen and chloride levels and the presence of sodium. A mechanism based on hot-salt stress-corrosion cracking is proposed and the implications for service components are discussed.

show abstract

supporting

confidence: 88%

mentioning

confidence: 97%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Environmentally assisted fatigue crack nucleation in Ti–6Al–2Sn–4Zr–6Mo

et al. 2015

View full text Add to dashboard Cite

show abstract

“…On breaking this passive layer, un-oxidised titanium beneath the patch may react with the HCl, producing titanium-alloy chlorides and atomic hydrogen that can "charge" the parent [2,11,34,35,39,42]. Thermodynamic analyses indicate that HCl preferentially attacks aluminium and tin in the alloy [39,43,44], generating more hydrogen than from attack of the titanium alone [39].…”

Section: Discussion -Mechanism and Chemistrymentioning

confidence: 99%

Understanding the “blue spot”

Saunders

Chapman

Walker

et al. 2016

Engineering Failure Analysis

View full text Add to dashboard Cite

During hot component fatigue tests there have been two cases of low life crack initiation of gas turbine rotating parts manufactured from the Titanium alloy Ti-6246. Both exhibited a small (~0,1mm) elliptical "blue spot" at the origin. Through validated striation count work and fracture mechanics it was established that fatigue had propagated with a near-nil initiation life. Early investigation suggested that the "blue spot" was possibly a region of stage 1 fatigue growth, and was therefore a material behaviour concern with potential implications for service. During an investigation of a later cracking incident in this alloy, subsequently shown to have resulted from Stress-corrosion cracking (SCC), near-identical fractographic characteristics to that seen in the "blue spot" were found that subtly differentiated it from stage 1 fatigue. Also, similar "blue spots" have since been identified on Ti6246 Laboratory hot LCF test specimens and found to have been due to contamination by NaCl, through the application of focussed long-term EDX examination and other novel chemical analyses techniques. By the application of those techniques, fractography, and comparison against these specimens, Rolls-Royce and Imperial College London have collaborated to show that the original two component "blue spots" were subtle examples of NaCl-related Hot Salt Stress-Corrosion Cracking (HSSCC). Such cracking has not been found to occur in service components, due to air pressure within the engine, and the effect is therefore confined to Laboratory and component tests at near-atmospheric pressure or below.

show abstract

Effect of plasma electrolytic oxidation on the hot salt corrosion fatigue behavior of the TC17 titanium alloy

Shi

Liu

Zhang

et al. 2021

Materials & Corrosion

View full text Add to dashboard Cite

In this paper, the effect of plasma electrolytic oxidation (PEO) on the hot salt corrosion fatigue (HSCF) behavior of the TC17 titanium alloy at 420°C was investigated. Through microstructure characterization and fatigue fracture analysis, combined with a comparative study of its hot salt corrosion behavior, the mechanism of PEO on HSCF behavior was also investigated. The results showed that the high‐temperature fatigue resistance of the TC17 titanium alloy was significantly reduced by the deposition of 0.4 mg/cm2 of solid NaCl compared with that without a salt coating. This behavior was observed because the corrosion pits caused by hot salt corrosion promoted the initiation of fatigue cracks, and hydrogen penetration promoted the growth of fatigue cracks. However, the HSCF resistance of the TC17 alloy with the PEO ceramic coating could be effectively increased. This was because the PEO ceramic coating with high bonding strength and good compactness effectively inhibited hot salt corrosion damage and delayed the formation of the resident slip zone and hydrogen permeation, thereby inhibiting the initiation and propagation of fatigue cracks.

show abstract

An electrochemical model for hot-salt stress-corrosion of titanium alloys

Cited by 19 publications

References 7 publications

Environmentally assisted fatigue crack nucleation in Ti–6Al–2Sn–4Zr–6Mo

Environmentally assisted fatigue crack nucleation in Ti–6Al–2Sn–4Zr–6Mo

Understanding the “blue spot”

Effect of plasma electrolytic oxidation on the hot salt corrosion fatigue behavior of the TC17 titanium alloy

Contact Info

Product

Resources

About