Microstructural Observation of The ’ Precipitation and Growth in Ta Containing Ni Based Superalloys

Superalloy of IN 718- the Ni-Cr-Fe based superalloys with Nb as one of the main strengthening elements- has been widely used in tubine gas components operating at medium temperature range (up to 650oC) because of its excellent mechanical properties, good workability and weldability and low cost. However, precipitation of incoherent  phase after long exposure limits the application temperature of the superalloys under 650oC. Our work is concerning to develop new γ’-strengthened alloys precipitation phase inherently has higher thermal stability than γ’’ γ’ phase precipitate phase. This paper reports the preliminary results on the effect of Ta -the potent alloying element- on precipitation and coarsening of γ’ phase of Ni-Al-Ta ternary alloy as the basic system in superalloys. Experimental results show that the alloy containing Ta revealed the cuboidal γ’ precipitates after aging treatment. The increasing of Ta/Al ratio of the from 0.14 in the alloy 1 to 0.42 in the alloy 2 leads the increasing of γ’ precipitate size. The splitting phenomenon is observed on the aloy 2 after solutionizing at 1100oC for 3 h and subsequent aging at 750oC for 20 h. Prosiding Seminar Material Metalurgi 2009