Treatment process in which a steel material is subjected to hot isostatic pressing, the material being such that the grains of which it is composed comprise a matrix in which precipitates are incorporated and such that: i) the material comprises the following elements, as percentage by weight: - 16% to 20% of chromium, - 8% to 14% of nickel, - 0.001% to 0.030% of carbon, - 0.001% to 0.050% of oxygen, - 0% to 2% of manganese, - 0% to 3% of molybdenum, - 0% to 1% of silicon, - 0% to 0.11% of nitrogen, - 0% to 0.045% of phosphorus, - 0% to 0.05% of sulfur, - 0% to 0.0300% of aluminium, - 0% to 2% of manganese, - 0% to 3% of molybdenum, - 0% to 0.003% of vanadium, - 0% to 0.02% of cobalt, - 0% to 0.02% of titanium, - 0% to 0.02% of copper, - the remainder of these elements being constituted of iron; ii) the precipitates comprising at least one metallic element chosen from a metallic element M, a metallic element M', a metallic element M'', or mixtures thereof; the metallic elements being chosen independently of one another from yttrium, titanium, iron, chromium, tungsten, silicon, zirconium, thorium, magnesium, manganese, aluminium, hafnium, molybdenum, or mixtures thereof; the mean density with which the precipitates are distributed in the matrix of the material being between 2 precipitates/μm 3 and 100 precipitates/μm 3, said mean density being determined by counting via imaging by scanning electron microscopy or by transmission electron microscopy, the microstructure of the steel being such that the grains are equiaxial and the average size of the grains, measured according to the standard ASTM E112-10, being such that the mean of their greatest dimension "Dmax" and/or the mean of their smallest dimension "Dmin" is between 10 μm and 50 pm. i) the material comprises the following elements, as percentage by weight: - 16% to 20% of chromium, - 8% to 14% of nickel, - 0.001% to 0.030% of carbon, - 0.001% to 0.050% of oxygen, - 0% to 2% of manganese, - 0% to 3% of molybdenum, - 0% to 1% of silicon, - 0% to 0.11% of nitrogen, - 0% to 0.045% of phosphorus, - 0% to 0.05% of sulfur, - 0% to 0.0300% of aluminium, - 0% to 2% of manganese, - 0% to 3% of molybdenum, - 0% to 0.003% of vanadium, - 0% to 0.02% of cobalt, - 0% to 0.02% of titanium, - 0% to 0.02% of copper, - the remainder of these elements being constituted of iron; - 16% to 20% of chromium, - 8% to 14% of nickel, - 0.001% to 0.030% of carbon, - 0.001% to 0.050% of oxygen, - 0% to 2% of manganese, - 0% to 3% of molybdenum, - 0% to 1% of silicon, - 0% to 0.11% of nitrogen, - 0% to 0.045% of phosphorus, - 0% to 0.05% of sulfur, - 0% to 0.0300% of aluminium, - 0% to 2% of manganese, - 0% to 3% of molybdenum, - 0% to 0.003% of vanadium, - 0% to 0.02% of cobalt, - 0% to 0.02% of titanium, - 0% to 0.02% of copper, - the remainder of these elements being constituted of iron; ii) the precipitates comprising at least one metallic element chosen from a metallic element M, a metallic element M', a metallic element M'', or mixtures thereof; the metallic elements being chosen independently of one another from yttrium, titanium, iron, chromium, tungsten, silicon, zirconium, thorium, magnesium, manganese, aluminium, hafnium, molybdenum, or mixtures thereof; the mean density with which the precipitates are distributed in the matrix of the material being between 2 precipitates/μm 3 and 100 precipitates/μm 3, said mean density being determined by counting via imaging by scanning electron microscopy or by transmission electron microscopy, the microstructure of the steel being such that the grains are equiaxial and the average size of the grains, measured according to the standard ASTM E112-10, being such that the mean of their greatest dimension "Dmax" and/or the mean of their smallest dimension "Dmin" is between 10 μm and 50 pm.