Microstructure and Properties of Modified IN718 Alloy Added P and B

In this paper, a modified IN718 alloy added P and B was produced under industrial condition. The ingot macrostructure, microstructure and mechanical properties of forged bars and rolling bars were analyzed, and the properties were compared with conventional IN718. The results indicated that the as-cast structure of modified IN718 508 mm in diameter ingots with 0.02 wt.% P and 0.008 wt.% B addition is uniform, and no 'freckles', 'white spots' or other macro-segregation related defects were observed. When the grain size and 6 phases were kept similar to IN718, the tensile strength of the modified IN-718 bar with a 250 mm diameter is comparable, but the stress rupture property at 650 degrees C/690 MPa of the modified IN718 is significantly higher, about 2 times. And the tensile properties and the stress rupture properties at 650 degrees C/725 MPa of the rolled bars with a 45mm diameter of the two alloys exhibit the same regulation. The fracture surfaces of the stress rupture samples of both the modified and conventional IN718 alloys were oberserved to be composed of the crack initiation and propagation area and the final transient fracture area.