A method for joining substrates of the active metals, such as niobium, tantalum, and titanium, and alloys of the active metals is disclosed. The substrates are joined in a deposit zone traversing areas to be joined on the substrates. The areas to be joined are formed to have deposit receiving surfaces that will form a diffusion bond with a spray deposit. An active metal or an alloy of an active metal compatible with the substrates to be joined is provided as a powder for plasma spraying. The substrates are disposed in a radio frequency low-pressure plasma-spray apparatus to receive a spray deposit on the deposit receiving surfaces in the zone. The deposit receiving surfaces are preheated and cleaned by passing the surfaces in heat coupling relation by the plasma, and placing the substrates at a negative DC potential relative to the plasma. A transferred arc from the radio frequency plasma-spray apparatus to the surfaces is generated that cleans the surfaces. The compatible powder is low-pressure plasma-sprayed deposited onto the preheated and cleaned deposit receiving surfaces to at least form a deposit in the zone that is diffusion bonded to the deposit receiving surfaces.