Oxidation-assisted cracking (OAC) is a particular type of damaging process called “dynamic embrittlement”. Dynamic embrittlement is a fragile rupture process which implies the ingress, diffusion and segregation of embrittling elements at the grain boundaries leading to their debonding. These embrittling elements may be provided by the material itself, as in the case of sulfur in steels or tin in copper alloys, or by the material's environment, notably oxygen's partial pressure. One of the most-studied cases is OAC for nickel-based alloys for which the penetration and segregation of oxygen, often associated with intergranular oxidation, change the crack propagation mode from transgranular to intergranular and significantly increase the crack propagation rate. In the aeronautical industry, as in the nuclear industry, this phenomenon is responsible for numerous cases of in-service cracking. To study the propagation rate's susceptibility to the chemical environment, numerous mechanical tests are conventionally performed in laboratory air or a vacuum. The propagation rates measured during low-frequency fatigue-creep tests (trapezoidal mechanical cycle: 10s-300s-10s) in the case of alloy 718 tested at 650°C in different environments.