Overclad

Overclad, or overcladding, is the process of applying an additional protective layer of material over an existing cladding or substrate. The goal is to enhance surface properties such as corrosion resistance, wear resistance, or high-temperature performance, or to repair or extend service life of a component without replacing the base material. The overlayer is typically a corrosion-resistant alloy or wear-resistant carbide-containing material chosen for compatibility with the substrate and service environment.

Common applications include oil and gas pipelines, chemical processing equipment, power plant components, and other settings where the base metal needs extra protection. Overclading is used to resist aggressive media, high pressure, and abrasive conditions, or to join dissimilar metals when full replacement is impractical.

Methods include welding overlays (GMAW, SAW, or FCAW), which deposit a layer of alloy onto the substrate; thermal spraying (high-velocity oxy-fuel or plasma spraying); explosive cladding or roll bonding for specific material combinations; and diffusion bonding under controlled heat treatment.

Quality and challenges involve ensuring metallurgical bonding at the interface, controlling dilution and thickness, managing residual stresses, and preventing cracking or delamination. Inspection methods include radiography, ultrasonic testing, dye penetrant testing, or eddy current testing.