Electrocodeposition and Mechanical Properties of Nickel-Tungsten Carbide Cermets

Abstract

Electrocodeposition of tungsten carbide (WC) particles (average size of 2 μm) from all-chloride nickel electroforming bath has been investigated with respect to particle concentration in the electrolyte (0.05 to 0.20 vol%) and current density (1200–2400 A/m²). Both the sediment codeposition (SCD) and conventional electrocodeposition (CECD) techniques have been utilized. The SCD gives 1.2 to 1.8 times higher incorporation of particles in the deposit as compared with the CECD. The Guglielmi’s model for the mechanism of codeposition is found to be valid for both SCD and CECD processes and they yield the same value of adsorption constant k(8.9). Composites produced contain 37 to 59 vol% tungsten carbide and in this range microhardness increases linearly (270 to 560 VHN), whereas tensile strength decreases (568.8 MPa to 191.2 MPa) with the content of WC . Annealing of the deposited composites shows that the recovery process takes place around 523 K (250°C) and the recrystallization appears to be inhibited due to the presence of WC particles.