Investigation of tribological and corrosion performance of electroplated hard chromium coating on 17-4 PH steel

Electroplated hard Cr-coated 17-4 PH stainless steel is regularly used in various parts of fuel handling system of nuclear reactors. In this study, the Cr-coated samples were investigated in detail for the coating adhesion using micro-scratch tester and ball indentation. Tribological investigation of the Cr coating was done in a reciprocating ball-on-plate dry sliding geometry against SS 440C ball counterbody. The wear and coefficient of friction (COF) tests were performed under five different loading conditions (3, 5, 7, 9 and 11 N) and three different sliding frequencies (5, 10 and 15 Hz). Wear scars on chromium coating were examined in detail by FESEM and 3D optical profilometer to understand the wear mechanism. It was observed that beyond 7 N critical load, the coating was prone to wear out drastically. Corrosion rate of the coating was estimated in 3.5 wt% NaCl solution by potentiodynamic experiment.