Overmoulding method

An overmoulding method for making an overmould (2) forming a decoration to be added to a part (1) or a part itself, said overmould (2) being made of an at least partially amorphous metal alloy (8), the method comprising the following steps:

• providing an ébauche (3) used as an injection tool with a first face (3a) to be overmoulded and a second face (3b) acting as an entry point for injecting the liquid metal alloy (8), said ébauche (3) being provided with at least one through hole (4) extending between the first face (2a) and the second face (3b) and opening out onto the overmould (2) to be made, the through hole (4) forming a channel (5) for injecting the metal alloy (8), said ébauche (3) being made of a first material with a thermal effusivity less than or equal to 7,000 W K−1 m−2 s½, preferably less than or equal to 3,500 W K−1 m−2 s½, or being at least partially plated with a layer made of said first material,
• providing an injection mould (6), said injection mould (6) and/or the ébauche (3) comprising an impression (7, 13) forming the negative of the overmould (2) to be made,
• positioning the ébauche (3) inside the injection mould (6) with the through hole (4) arranged facing the impression (7) of the injection mould (6) if said injection mould (6) comprises an impression (7),
• injecting the liquid metal alloy (8) from the second face (3b) of the ébauche (3) through the through hole (4) opening onto the impression (7, 13) to obtain the ébauche (3) with the overmould (2),
• unmoulding the ébauche (3) with the overmould (2),
• detaching the overmould (2) from the ébauche (3) to form the decoration to be added or the part itself.