The removal of oil-based contaminants from microcavities with narrow a
pertures and comparatively long axial dimensions presents a number of
challenges in an industrial production line environment. Traditional s
olvent-based approaches are costly to implement, inefficient in cleani
ng such microcavity geometries, and increasingly unacceptable from an
environmental standpoint. An attractive alternative is to employ high-
energy laser pulses to selectively remove the contaminants without int
roducing damage to the component undergoing the cleaning procedure. Th
is paper will present results of initial oblation trials on example in
dustrial oil-based organic contaminants whose residues within microcav
ities in steel-based components are to be removed. At present, higher
order lines from a frequency tripled/quadrupled Nd:YAG laser are used
to study the optimum fluence for removal of the oil-based contaminant
without inflicting damage to the steel. Absorption spectroscopy of the
contaminant fluid indicates that photon wavelengths shorter than simi
lar to 370 nm will interact with the material. Initial results show ch
at the required intensity at 355 nm (> 25 J/cm(2)) also damages the ty
pe of steel under investigation, but that exposure to even single puls
es at 266 nm (similar to 100 mJ/cm(2)) shows adequate removal of the c
ontaminant without significant damage to the steel. Monitoring of the
removal process is achieved through exploitation of the blue fluoresce
nce of the oil-based contaminant that occurs as a result of ultraviole
t pumping. (C) 1998 Elsevier Science B.V.