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How to measure bond strength of plating
Dears,
I would like to know is there any instrument by which we can measure the bond strength of our tri metal plating on journal bearings, the thickness of the plated layer is around 15-30 microns .
Engineer - India
April 24, 2011
There is a direct method where the bond strength can be precisely measured that is common for thermosprayed and other coatings that are not metallurgically bonded. It is based on a metal rod that is glued to the coated surface and pulled apart. Its disadvantage is that the maximum permissible value is limited to the actual tensile strength of the epoxy used (theoretically 700 Kg/mm2, practically only 400-500 Kg/mm2). Indirect measurements that involve deformation of calibrated coupons and Passed/Not Passed qualification are common for plating. An example of this would be the bend test.
G. Marrufo-Mexico
Monterrey, NL, Mexico
First of two simultaneous responses -- April 26, 2011
Second of two simultaneous responses -- April 27, 2011
I'm not sure if there is any good way to measure the actual bond strength.
Many years ago, I routinely checked the bond of Lead-tin, and lead-tin-copper plated onto leaded bronze and aluminum alloys. We used two tests: the scotch tape test which was non destructive, and a scalpel test which was destructive, but more informative.
consultant - Cleveland Heights, Ohio
Like Lyle, I used to work in a bearing plating facility and we also tested the lead-tin and lead-tin-copper overlays by either a "Scotch tape" test of a cross hatch test. The scotch tape test just checked that the coatings were adherent, but the cross hatch test involved scoring the white metal with diamond shaped cuts about 5 mm apart and then applying an adherent tape and rapidly remove it in one continuous movement; if any overlay stuck to the tape, the batch was scrapped.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
April 28, 2011
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