| Inconel 713 LC cast superalloy has excellent high-temperature creep properties,thermal fatigue properties and oxidation resistance.It is mostly used to manufacture turbine rotor blades,guide vanes and other high-temperature components of aeroengines.However,Inconel 713 LC alloy has poor weldability and is prone to welding cracks,which is not conducive to the welding repair of damaged components.Therefore,based on the research background of surfacing repair of aeroengine turbine rotor blade profile loss,the surfacing test of Inconel 713 LC superalloy was performed by micro beam plasma arc welding.The effects of welding process conditions on the microstructure and susceptibility of welding hot cracks of surfacing joints were studied and analyzed,and the mechanical properties of the welded joints were experimentally studied.The results showed that:(1)The as-cast base metal of the Inconel 713 LC superalloy presents dendritic structure.from the near surface area of the fusion line area in the joint surfacing area,the grains of the surfacing area gradually grow from small cross-shaped to stagger columnar dendrites and cellular crystal.The distribution of elements in the fusion line area is even,and the surfacing area is well combined with the base metal.The microstructure of heat affected zone is no longer presents a dendritic structure due to the influence of welding temperature field,mainly organized as γ-Ni matrix,fine γ′ Strengthening phase,small amount(γ+γ′)eutectic phase and the MC phase precipitated in chains.(2)The welding cracks of Inconel 713 LC superalloy surfacing joint mainly appear in the heat affected zone of the joints,which belong to liquefaction crack,and the cracks extend along the carbides and eutectic phases precipitated at the grain boundary.The main reasons for the formation of welding cracks are: Affected by the welding heat input,the larger carbides and eutectic phases at the grain boundary of the heat affected zone undergo component liquefaction,Nb,Mo and other elements segregate to the grain boundary to form liquefied film,the liquid film is torn by stress during the cooling process to form cracks.(3)The test has proved that: By(1)adjusting the welding process parameters to control the welding heat input,(2)forcing cooling conditions during the welding process to shorten the high temperature residence time of the joint,(3)using pulse current welding,(4)carrying out solid solution treatment on the base metal before welding to improve the original state of the base metal,we can effectively inhibit the liquefaction of grain boundaries in the heat affected zone of the joint and the segregation of elements such as Nb and Mo during the welding process,so as to inhibit the generation of welding cracks and obtaining defect-free Inconel 713 LC welded joints.(4)The mechanical properties of Inconel 713 LC weld samples repaired by plasma arc surfacing can reach the level close to that of the base metal as a whole.Among them,the hardness of the surfacing area of the welded joint is lower than that of the base metal,the overall hardness transition of the joint is stable,and the base metal and the surfacing area are well combined.The weld tensile strength is close to the base metal,the yield strength is89.6% of the base metal on average,and the average tensile strength reaches 91.0% of the base metal.In addition,the fatigue performance of Inconel 713 LC weld sample is good,which can be maintained at the same level as the base metal,and the surfacing has no significant impact on the service life of the base metal.It is proved that it is feasible to repair the damaged Inconel 713 LC superalloy components by plasma arc surfacing. |
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