Research status of cladding welding protection technology for water-wall of power plant boiler

The water-wall of power plant boiler undergoes thinning and bursting under the effects of high temperature oxidation, high temperature corrosion and erosion wear, which affects the safely operation of the boiler. Therefore, corrosion and erosion resistant protection must be carried out. This article reviews the cladding welding technologies for water-walls. The commonly used cladding welding processes for water-walls includes gas metal arc welding, cold metal transfer welding, laser cladding and so on. Cold metal transfer cladding welding has a low dilution rate and is suitable for on-site operation, which is a very promising cladding welding method for water-wall protection. The commonly used water-wall cladding materials includes austenitic stainless steels and nickel-based alloys. Inconel 625 alloy has excellent comprehensive properties and is the most commonly used one for cladding welding of water-wall. Inconel 625 alloy cladding layer exhibits a typical austenite dendritic structure with secondary phase precipitation in the interdendritic region. The austenitic stainless steel cladding layer has a transition zone with dual phases of martensite and austenite on the interface with the substrate. The Inconel 625 alloy or austenitic stainless steel cladding layer have a certain tendency of solidification crack. Controlling the impurity content and dilution rate in the cladding layer can prevent the occurrence of solidification crack. The cladding welding deformation water-wall is significant, which can be controlled by using a low heat input and appropriate cladding sequences.