High Energy Beam Surface and Interface Modification of Thermally Sprayed Coatings

The application of thermally sprayed coatings is often limited by their porosity as well as their low adhesion. A new approach for high energy beam surface treatment of thermally sprayed coatings is presented using simultanously a lower power level for continuous remelting and pulses of higher power in order to get coatings with good corrosion behaviour and improved adhesion. This technology is applied to titanium as well as to NiCr-coatings on steel substrates. The investigations prove that remelted thermally sprayed coatings with a smooth and dense surface layer, followed by a heat treated section of the coating and a reaction zone at the substrate/coating interface can be obtained. Therefore, a change in chemical composition of the coating is avoided, while at the same time the bond strength of the remelted coatings can be influenced by metallurgical reactions at the interface zone.