Accession Number : ADA259884
Title : Nondestructive Evaluation of Electrodeposited Chromium
Descriptive Note : Final rept.
Corporate Author : ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
Personal Author(s) : Todaro, Mark E
Report Date : Nov 1992
Pagination or Media Count : 16
Abstract : Benet Laboratories is pursuing methods for nondestructively evaluating the quality and adhesion of electrodeposited chromium coatings on the bore of large caliber gun tubes. The Army currently has no suitable means for testing such coatings nondestructively. A poor quality or poorly adherent coating shows up only when several test rounds are fired through the tube, removing portions of the coating and exposing the steel underneath. Recent in- house work has investigated both photothermal and ultrasonic methods. The photothermal method involves briefly heating the surface of the chromium with a laser pulse. After the initial heating, the surface temperature decreases as heat diffuses into the coating and substrate. The characteristics of the coating, interface, and substrate affect the surface temperature profile in distinct ways. The temperature of the surface can be measured by observing the emitted infrared radiation with a focused detector or an infrared scanner. Although no experimental data using the photothermal technique has been obtained yet, a one-dimensional finite difference algorithm was used to model temperature changes on the surface of a chromium coating on steel due to an incident energy pulse. The model verifies that with a suitable choice of laser pulse width, one could measure the thermal characteristics of the coating and detect the presence of a thermal discontinuity at the interface.
Descriptors : *NONDESTRUCTIVE TESTING , *METAL COATINGS , TEST AND EVALUATION , ALGORITHMS , DENSITY , MODELS , INTERFACES , SUBSTRATES , STEEL , CHROMIUM , LOW DENSITY , HEATING , COPPER , ULTRASONICS , QUALITY , PROFILES , LASER APPLICATIONS , INTERFEROMETRY , PHOTOTHERMAL PROPERTIES , MECHANICAL IMPEDANCE , SCANNERS , ELECTRODEPOSITION , BORES , STRESS WAVES , SELECTION , SURFACE TEMPERATURE , DISCONTINUITIES , HEAT , INFRARED RADIATION , REFLECTION , ADHESION , ONE DIMENSIONAL , GUN BARRELS , RADIATION , EXPERIMENTAL DATA , DETECTORS
Subject Categories : Coatings, Colorants and Finishes
Mfg & Industrial Eng & Control of Product Sys
Distribution Statement : APPROVED FOR PUBLIC RELEASE