Poster Session

Homogeneity of wear resistant MMC coatings deposited by plasma transferred arc welding

Tonya Wolfe, PhD student in Materials Engineering

Supervisor - Dr. Hani Henein

Wear of mining equipment is expensive in Canada. To extend the component life, a composite coating is applied onto a substrate by plasma transferred arc welding (PTAW). The coating is a metal-matrix composite (MMC): a combination of a hard ceramic particulate reinforcement (WC) and a tough corrosion- and wear-resistant nickel alloy as the matrix. The coating life is shorter than expected, as it either spalls off or wears prematurely.

The PTAW process is complex: the effect of operating variables on the coating life differs with varying coating thickness, matrix alloy, and industrial application. As a result the optimization of the PTAW process variables are empirically determined. A desirable coating consists of the following characteristics: high toughness, high wear abrasion, and homogeneity of reinforcement particles throughout the thickness. This project only addresses the control of homogeneity of the PTAW coatings through investigation of the solidification of the coating in terms of arc heat input and cooling rates.

Instrumented PTAW experiments were carried out and related to microstructural characteristics of MMC deposits. The temperatures of the substrate and coating are measured using thermocouples, infrared thermography and laser reflectometry, and are correlated to the degree of settling of the WC particles in the MMC. It will be shown that current, plasma gas flow and travel speed have a significant effect on the homogeneity of the coating and arc heat input.