Product nitriding process using hot isostatic pressure

A method of improving the mechanical properties of metallic products, especially for surface hardening, is disclosed. The method comprises product nitriding in a gas atmosphere containing nitrogen and/or compounds containing nitrogen in the presence of a catalyst. Together the product and the catalyst are subject to Hot Isostatic Pressing (HIP), while observing the pressure and temperature, to achieve a dislocations density in the product s volume that satisfies the conditions required for transition of a part of the product substance into the positron state. The metal is preferably an alloy, especially steel. The Hot Isostatic Pressing preferably uses a pressure between 100 and 300 MPa, and a temperature between 1500 and 2500ºC. The catalyst may use Group 1 elements, which may produce highly active media and/or compounds in the gas atmosphere and initiate transient phases with positronium in the product s volume. The product may be hollow, with its interior surface forming part of the Hot Isostatic Pressing area, in which catalyst is provided, so that nitriding takes place from the interior surface.