Fatigue and fracture toughness characteristics of laser rapid manufactured Inconel 625 structures

Fatigue crack growth and fracture toughness characteristics of laser rapid manufactured (LRMed) Inconel 625 compact tension specimens of thickness 12 and 25 mm were investigated. Fatigue crack propagation in all the specimens investigated in the stress intensity range (ΔK) of 14–38 MPa√m, exhibited stage II crack growth in Paris’ regime with nearly same slopes of crack growth per cycle versus ΔK plot. Fatigue crack growth rates in the LRMed specimens of present study were found to be lower than the reported values for wrought Inconel 625 in the ΔK range of 14–24 MPa√m and above this range they tended to coincide. X-ray diffraction patterns of the fractured surfaces revealed that the crack propagated along the growth direction of the specimens which was predominantly along the (1 1 1) plane. The fracture toughness values (J0.2) for LRMed Inconel 625 specimens were found to be in the range of about 200–255 kJ/m2. The LRMed specimens exhibited stable crack growth during the J-integral test.