Part composed in whole or in part of a steel material the grains of which it is composed comprise a matrix in which precipitates are incorporated and such that: i) the material comprises, as percentages by weight, the following elements: - 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, - 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 equiaxed and the average grain size, measured according to the standard ASTM E112-10, being such that the average of their largest dimension "Dmax" and/or the average of their smallest dimension "Dmin" is between 10 μm and 50 μm. i) the material comprises, as percentages by weight, the following elements: - 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, - 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, - 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 equiaxed and the average grain size, measured according to the standard ASTM E112-10, being such that the average of their largest dimension "Dmax" and/or the average of their smallest dimension "Dmin" is between 10 μm and 50 μm.