Abstract: A method is provided for depositing and thermally diffusing a boride or a carbide of a refractory metal on a substrate of a workpiece. A layer of the refractory metal is deposited on the substrate. At least one of the elements boron and carbon is deposited from a source other than the workpiece on the workpiece having the refractory metal layer. The workpiece is heated at a temperature and for a time period sufficient to diffuse at least a portion of the deposited refractory metal into the substrate and at least a portion of the deposited boron or carbon into the refractory metal layer and the substrate to form a substantially uniform and metallurgically bonded layer of the boride or carbide of the refractory metal on the substrate.