Fracture properties of multiphase alloy MP35N

This paper addresses the fracture properties of commercially cold-drawn (53%) MP35N (35% Co, 35% Ni, 20% Cr, and 10% Mo) in both the cold-worked and the cold-worked and aged conditions. MP35N is a superalloy that exhibits a remarkable combination of high strength (about 2 GPa) and high fracture toughness (about 100 MPa m ). The fracture toughness of MP35N was investigated systematically, with particular attention to the influence of the post deformation aging heat treatment, the sample thickness, the orientation of crack plane and the direction of crack propagation with respect to the drawing direction in the sample. These measurements yielded the following important results: (1) The plane strain fracture toughness of the commercially cold-drawn MP35N is about 120 MPa m , and is about 110 MPa m in the cold-drawn and aged condition. (2) The plane stress fracture toughness values for the cold-drawn MP35N were significantly lower than the corresponding values for the cold-drawn and aged material, in spite of the fact that the later had a higher strength value. (3) The direction of the crack propagation did influence the fracture toughness, reducing its value significantly in T–L direction, as compared with values in T–T and L–T directions.