A method for controlling the crystal orientation of at least one crystallographic grain of a turbo engine part (10, 16, 28, 38, 40), comprising the steps of: a) emitting a beam of electromagnetic radiation through an elementary volume of the part and record diffraction information on the electromagnetic radiation passing through the part; b) repeating step a) on a given area of the part, c) determining a crystal spatial orientation of each of said elementary volumes and deducting the presence of at least one first crystallographic grain for which the elementary volumes are oriented according to the same crystallographic orientation; d) calculating the angular difference ( α 1) between the crystal spatial orientation of said first grain and a predetermined direction taken from the part and comparing it to a first predetermined threshold value; e) determining a state of use of the part. said step e) further comprising the following steps: i. identifying in the given area the presence of at least a first and second distinct crystallographic grain from the diffraction information; ii. determining a spatial orientation of said second grain of the part from the diffraction information; iii. calculating the angular deviation ( α 2) between the spatial orientation of said second grain and said predetermined direction of the part and comparing it to the first predetermined threshold value; iv. calculating the angular difference ( β) between the spatial orientation of said first grain and the spatial orientation of said second grain and comparing it to a second predetermined threshold value; v. determining the state of use of the part in steps d), iii) and iv). a) emitting a beam of electromagnetic radiation through an elementary volume of the part and record diffraction information on the electromagnetic radiation passing through the part; b) repeating step a) on a given area of the part, c) determining a crystal spatial orientation of each of said elementary volumes and deducting the presence of at least one first crystallographic grain for which the elementary volumes are oriented according to the same crystallographic orientation; d) calculating the angular difference ( α 1) between the crystal spatial orientation of said first grain and a predetermined direction taken from the part and comparing it to a first predetermined threshold value; e) determining a state of use of the part. said step e) further comprising the following steps: i. identifying in the given area the presence of at least a first and second distinct crystallographic grain from the diffraction information; ii. determining a spatial orientation of said second grain of the part from the diffraction information; iii. calculating the angular deviation ( α 2) between the spatial orientation of said second grain and said predetermined direction of the part and comparing it to the first predetermined threshold value; iv. calculating the angular difference ( β) between the spatial orientation of said first grain and the spatial orientation of said second grain and comparing it to a second predetermined threshold value; v. determining the state of use of the part in steps d), iii) and iv). i. identifying in the given area the presence of at least a first and second distinct crystallographic grain from the diffraction information; ii. determining a spatial orientation of said second grain of the part from the diffraction information; iii. calculating the angular deviation ( α 2) between the spatial orientation of said second grain and said predetermined direction of the part and comparing it to the first predetermined threshold value; iv. calculating the angular difference ( β) between the spatial orientation of said first grain and the spatial orientation of said second grain and comparing it to a second predetermined threshold value; v. determining the state of use of the part in steps d), iii) and iv).