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Introduction
The quality of a sprayed metal deposit is known to be related to
the nature of the prepared surface of the base metal. Grit blasting is
a common method of surface preparation, and the actual profile or surface
contour of the prepared surface can be varied considerably by variation
in blasting conditions. The exact requirements of an acceptable surface
have never been accurately stated, although a degree of undercut is.
considered essential.
The object of the present work is to develop a non-destructive
method for the assessment of blasted mild steel surfaces in terms of
suitability for metal spraying. Such a method needs to combine simplicity
and speed, so that it can be used by normal inspection personnel without
delaying production. Preferably the method should incorporate a 'failsafe!
mechanism..
A number of possible assessment methods have been considered, but
attention has been largely concentrated on measurement of the diffuse
reflectivity of blasted surfaces. In reality, of course, this is simply
an attempt to replace the eye in visual inspection with an instrument,
and so remove the human element. Results have been reasonably encouraging,
but it is obvious that many more samples need to be examined before a true
judgement can be made.
Some difficulty has been encountered in deciding the requirements for
an acceptable surface. For this reason, a part of the experimental effort
has been devoted to the examination of blasted surfaces, and to the measurement
of bond strength after metal spraying.
A brief review of literature has also been included. |
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