Composite gear blank

A method of manufacturing a composite gear blank, comprising a rigid centerpiece and an outer part made of a plastic material, said centerpiece being substantially disk-shaped with two disk-faces substantially parallel to each other, said outer part being cast around a peripheral surface of said centerpiece, wherein said composite gear blank has the following properties:

• a) when determined at a temperature of up to 25° C.:
• a normal adhesion strength SN between outer part and centerpiece of at least 17 MPa;
• a shear adhesion strength SS between outer part and centerpiece of at least 16 MPa;
• and
• b) when determined at a higher temperature of up to 120° C.:
• a normal adhesion strength SN between outer part and centerpiece of at least 11 MPa;
• a shear adhesion strength SS between outer part and centerpiece of at least 16 MPa;
• wherein said normal adhesion strength SN is determined by applying a radially outward load with a constant velocity of 5 mm/min and wherein said shear adhesion strength SS is determined by taking the lower value of:
• i) a tangential adhesion strength ST obtained by applying a tangential load with a constant velocity of 3 rad/min, and
• ii) an axial adhesion strength SA obtained by applying an axial load with a constant velocity of 1 mm/min,
• comprising the steps of:
• a) providing at least one rigid centerpiece having a structured peripheral surface to be surrounded by said plastic material;
• b) surface roughening said peripheral surface;
• c) surface conditioning the centerpiece;
• d) placing the centerpiece in a mold;
• e) optionally inertizing the mold by flushing with an inert gas;
• f) adding a liquid reactive mixture into the mold until the liquid reaction mixture at least partially surrounds the centerpiece;
• g) applying a static pressure to the mold containing the liquid reactive mixture;
• h) polymerizing the reactive mixture to form said outer part;
• wherein surface conditioning comprises applying an organofunctional silane compound onto the peripheral surface and wherein, after step h), the centerpiece is subjected to a controlled heating step so as to locally melt the plastic material in a region adjacent to the centerpiece, followed by forced cooling of the centerpiece.