Phosphorus Particle Composite Plating with Ni–P Alloy Matrix

Abstract

Ni–P alloy films containing phosphorus particles (called “Ni–P alloy composite films”) were fabricated by electrodeposition and were subsequently subjected to heat-treatment. Their compositions and microstructures were characterized, and their friction properties were evaluated using a ball-on-plate method. Composite electroplating in the nickel sulfate and chloride bath containing phosphorus acid and micrometer-sized phosphorus particles resulted in the Ni–P alloy coating with enhanced deposit phosphorus content. The phosphorus content of the films increased with increasing phosphorus particle concentration in the composite plating baths, reaching a maximum value of 29.0 atom %. The phosphorus particles were homogeneously distributed in this Ni–29.0 atom % P alloy composite film. Heat-treatment converted the phases of the alloy composite films from an amorphous phase to stable crystalline phases, which are the same as those in the Ni–P binary alloy phase diagram. The friction coefficients of the Ni–P alloy films increased with increasing cycle number, whereas those of the Ni–P alloy composite films remained relatively constant. The alloy composite films had lower friction coefficients than the Ni–P alloy films both before and after heat-treatment. These results indicate that phosphorus particles are beneficial for maintaining a lower and stable friction coefficient during the ball-on-plate reciprocating friction test.