Engine Titanium Consortium - Center for Nondestructive Evaluation ...

C2b – Alkaline De-rust Solution B
C5 – Alkaline Gel Cleaner
B1– Plastic media blast (at 80 and 40 psi) for 30 sec
• Soot on nickel-based specimens
C3 – Alkaline De-rust Solution A
C7a – Ultrasonic w/Alkaline De-rust Solution B
B1– Plastic media blast (at 80 and 40 psi) for 30 sec
• Varnish/Coke on nickel-based specimens
C3 – Alkaline De-rust Solution A
C5 – Alkaline Gel Cleaner
C7a – Ultrasonic w/Alkaline De-rust Solution B
B1– Plastic media blast (40 psi) for 30 sec
Visually, almost all of the specimens were evaluated as having a surface that appeared to be clean
following the initial cleaning attempt. At the very least, two out of the three specimens for a
particular contaminate/cleaning method combination were assessed as visually clean. However,
crack crevice cleaning as evaluated by brightness was a different story. Many of the specimens
showed reduced brightness with respect to baseline brightness and in some cases no indication
could be discerned either by photometer or by a more sensitive though qualitative visual black light
examination.
The C4 four-step alkaline process for nickel-based materials (alkaline rust remover, acidic scale
conditioner, alkaline permanganate, alkaline rust remover) proved successful for removing all three
contaminants from the cracks and restoring much of the baseline fluorescent brightness. It was
somewhat less effective on nickel oxidation. However, no cleaning process for titanium proved as
effective as the four-step for nickel-based materials.
For removal of oxidation on titanium, the cleaning difficulty was partly due to the higher degree of
oxidation with to the nickel-based material. Oxidation on the titanium was estimated to be
equivalent to 5,000 hours of engine run. It represents a heavy amount of oxidation that is now
being seen on some of the hotter running titanium components.
In addition, the method for producing soot by suspending specimens, crack opening down, over hot
oil produced a blackened surface having somewhat of a sheen rather than a matte black finish.
This condition would more likely be found on turbine engine hot section parts, but probably not on
titanium cold section parts. The contaminant condition proved more resistant to some of the
cleaning methods than typical soot.
There were sometimes apparent inconsistent results for a particular contaminant/cleaning method
that may be related to three different crack sizes being used. That is, perhaps a chemical cleaning
method is more effective at removal of soot on a large, open crack than on a small, tight crack or
Quarterly Report – January 1, 2002 –March 31, 2002
print date/time: 6/6/2002 - 8:39 AM – Page 81