Evaluation of Residual Stresses, Grinding Burns and Heat Treat Defects Through Chrome Plating

Determining residual stresses and detecting material defects through coatings is difficult with conventional testing techniques. X-ray diffraction can be used for residual stress determination on bare surfaces of a variety of materials, but fails to give any indication of stress in the underlaying metal through coatings. Nital etching cannot be used to detect grinding burns unless coating is removed. To overcome these difficulties, magnetic Barkhausen noise technique was used to study the feasibility of determining stresses and detecting grinding burns and heat treat defects through chrome plating.

Test results suggest that the sensitivity of Barkhausen noise technique to defects and residual stresses through chrome is excellent up to plating thicknesses of 0.012 in. (0.3 mm). This technique can replace the presently used procedures to determine stress and to detect material defects through coatings.