Improved Hardness and Tribocorrosion Properties of Nickel Coatings By Co-Depositing ZrO2 Micro-Sized Dispersed Phase During Electroplating Process

Abstract

The tribocorrosion properties of ZrO2 – nickel microstrucured composite coatings have been studied in the following conditions: -Solution: 0.5M K2SO4 -Tribo corrosimeter: pin on disc connected with electrochemical cell. -Normal Force: 10N -Rotation Speed: 120 tours/min. The objectives of our study in principal are to fully understanding the tribocorrosion process kinetic and mechanism of composite coatings materials. The samples with coating on a top of a cylinder were installed in a cell, containing the electrolyte and electrodes, and mounted on a pin-on-disc tribometer, with the working surface of the specimen facing upwards. The counterbody (pin) was a corrundum cylinder (7 mm in diameter), mounted vertically on a rotating head, above the specimen. The lower spherical end (radius = 100 mm) of the pin, was then applied against the composite surface (disc) with an adjustable normal force. When rotation was applied, the end of the pin draws a circular wear track (16 mm in diameter) on the working composite surface. Both continuous and intermittent friction tests were carried out. In the intermittent tests, friction was applied periodically: during each cycle, friction was first applied for 2 seconds at 120 rpm (sliding speed 100 mm/second) under 10 N (average pressure 120 MPa for hertzian contact conditions) and then stopped during a latency time (20 or 200 s.). This mechanical solicitation was repeated over 2500 cycles. Some features of these tests reproduce the wear conditions of composite coatings in the intermittent friction, K2SO4 0.5M was used as corrosive and passivating electrolyte for tribocorrosion tests.