A machine for performing heat treatment of mechanical parts shaped like a solid of rotation, particularly for hardening railroad wheels or the like, comprising: - a tank, adapted to accommodate at least the portion of a mechanical part to be treated; - means for supplying a treatment fluid to said tank; - means for supporting the mechanical part in said tank so that the axis of said mechanical part is arranged substantially vertically; - first means for dispensing a treatment fluid, which are arranged in said tank and with a dispensing direction oriented toward the lateral surface of the mechanical part that is placed on said supporting means in said tank, said first dispensing means comprising first nozzles for dispensing said treatment fluid which face the lateral surface of the mechanical part arranged on said supporting means, first means being provided for moving said first nozzles along a direction with a radial component with respect to said main axis; - means for varying the position of the mechanical part with respect to the free surface of the treatment fluid, in liquid state, in said tank, said means for varying the position of the mechanical part with respect to the free surface of the treatment fluid, in liquid state, comprising means for the translation of said supporting means along a substantially vertical direction; - means for the actuation of said supporting means with a rotation movement about a main axis in order to rotate the mechanical part that is arranged on said supporting means with its axis at said main axis; - second means for dispensing a treatment fluid, which are arranged proximately to the bottom of said tank and with a dispensing direction that is oriented toward the surface of the mechanical part which is directed toward the bottom of said tank,t said second dispensing means comprising second nozzles for dispensing said treatment fluid which face the surface of the mechanical part, arranged on said supporting means, that is directed toward the bottom of said tank, second means being provided for moving said second nozzles along a direction with a radial component with respect to said main axis. - a tank, adapted to accommodate at least the portion of a mechanical part to be treated; - means for supplying a treatment fluid to said tank; - means for supporting the mechanical part in said tank so that the axis of said mechanical part is arranged substantially vertically; - first means for dispensing a treatment fluid, which are arranged in said tank and with a dispensing direction oriented toward the lateral surface of the mechanical part that is placed on said supporting means in said tank, said first dispensing means comprising first nozzles for dispensing said treatment fluid which face the lateral surface of the mechanical part arranged on said supporting means, first means being provided for moving said first nozzles along a direction with a radial component with respect to said main axis; - means for varying the position of the mechanical part with respect to the free surface of the treatment fluid, in liquid state, in said tank, said means for varying the position of the mechanical part with respect to the free surface of the treatment fluid, in liquid state, comprising means for the translation of said supporting means along a substantially vertical direction; - means for the actuation of said supporting means with a rotation movement about a main axis in order to rotate the mechanical part that is arranged on said supporting means with its axis at said main axis; - second means for dispensing a treatment fluid, which are arranged proximately to the bottom of said tank and with a dispensing direction that is oriented toward the surface of the mechanical part which is directed toward the bottom of said tank,t said second dispensing means comprising second nozzles for dispensing said treatment fluid which face the surface of the mechanical part, arranged on said supporting means, that is directed toward the bottom of said tank, second means being provided for moving said second nozzles along a direction with a radial component with respect to said main axis.