The present invention relates to tools and methods for disposing, coating, repairing, or otherwise modifying the surface of a metal substrate using frictional heating and compressive/shear loading of a consumable metal against the substrate. Embodiments of the invention include friction-based fabrication tooling comprising a non-consumable member with a throat and a consumable member disposed in the throat, wherein consumable filler material is capable of being introduced to the throat in a continuous manner during deposition using frictional heating and compressive/shear loading of the filler material onto the substrate. Preferred embodiments according to the invention include such tools operably configured for applying a force or displacement to the filler material during deposition. Especially preferred embodiments can include using various powder-type consumable materials or combinations during the deposition process to obtain a continuous compositional gradient in the filler material yielding a functionally graded coating on the substrate.