Method for manufacturing an ornamental hard material part provided with a polymer coating

A method for manufacturing an ornamental part, for a timepiece, the part at least partly comprising a hard material having a Vickers hardness greater than 1000 HV, the method comprising:

• a step of producing a precursor from a mixture of at least one powder material with a binder,
• a step of injecting the precursor into a mould in order to form a green body,
• a step of sintering said green body in order to form a body of the part from said hard material, and
• a step of depositing a polymer material coating on one face of the part, the deposition being carried out by moulding on the body by injection into the mould, the coating and the hard material being inseparable, wherein the polymer material is selected from the following list:
• POM, PA, PUR, PPS, ABS, PC,
• wherein a back of the part is formed of the polymer material during the coating deposition step such that the back of the part is a back of the timepiece.