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Abstract:The present study involves evaluation of fracture toughness (crack tip opening displacement) and Chapry impact toughness of Inconel 625 structures fabricated by laser based additive manufacturing. The results of fracture toughness are close to those reported for the Inconel 625 weld metal. The nature of the load-time traces of instrumented Charpy impact tests revealed that the alloy Inconel 625 in laser fabricated condition was associated with fully ductile behavior with Charpy-V notch impact energy in the range of 48-54 J. Stress relieving heat treatment at 950 °C for 1 hour has resulted in marginal improvement in the impact toughness by about 10 %, whereas no clear evidence of such improvement is seen in the CTOD fracture toughness. Fractographic examination of the Chapry specimens and the results of the instrumented impact tests imply that the mechanism of crack growth was propagation controlled under dynamic loading conditions. Dynamic fracture parameters were estimated from the instrumented impact test data and compared with the experimentally evaluated fracture toughness results.