Scratch testing of electrolytic nickel coatings on a carbon fiber reinforced plastic substrate

Abstract

A method for quantitative assessment of the strength of nickel coatings adhesion to CFRP KMU-11-M2.200 by the sclerometry method with the use of a laboratory scratch tester is proposed. The method has expanded capabilities due to the operation according to two loading programs and an additional technique for recording the moment of destruction of the coating by changing the scratch resistance force. The appearance and schematic diagram of the non-standard ST-01 scratch tester, developed at the STCU VIAM, are presented. Scratch testing of nickel coatings obtained by the traditional electrochemical method in a bath and by the method of local brushing was carried out, with two methods of pre-treatment of the carbon fiber surface before nickel plating being considered (sandblasting and nitric acid etching). The surface morphology was investigated by optical microscopy and the thickness of nickel coatings deposited in the bath and by brushing was determined. By combining the obtained scratches with the plots of the indenter load and the resistance force against the indenter displacement, the critical load is determined at which continuous destruction of the coating with delamination is recorded. Based on the formulas of P.Benjamin and K.Weaver, the adhesion strength of nickel coatings was calculated and it was shown that the adhesion strength of nickel coatings deposited in a bath is 1.6 times higher than that of coatings obtained by brushing. The results of scratch testing are presented, and the nature of the destruction of nickel coatings at an indenter position of more than 25 mm is described.

Keywords

• scratch tester
• sclerometry
• carbon fiber reinforced plastic
• nickel coating
• adhesive strength
• indenter
• microhardness