The present invention concerns methods and apparatus for forming a clad product, such as a clad pipe or tube. Particular embodiments include a method for metallurgically bonding cladding material onto a metal substrate, the method including a step of providing a metal substrate comprising a pipe or a tube having a cladding composition arranged along an interior surface of the substrate to form a coated substrate, the interior surface arranged within an interior cavity of the substrate. A further step includes inserting a heat source into an interior cavity of the substrate, the heat source comprising an infrared, microwave, or radio frequency heat source, the heat source being mounted on a heat source-retaining housing, the housing comprising a cantilevered structure. An additional step includes applying heat discharged from the heat source to the coated substrate along the coated interior surface until the cladding composition metallurgically bonds to the substrate.