Abstract: The invention concerns a method of making an article from silicon nitride powder and a fluxing agent. The method comprises hot pressing a first section of the silicon nitride article, transferring the pressed section to a further mould large enough to accomodate sufficient silicon nitride powder and fluxing agent to produce the other section of the article, and subsequently hot pressing the contents of the mould to solidify the silicon nitride powder and fluxing agent into the second section of the article which becomes bonded to the first section.

Abstract: A rotor for a gas turbine engine comprises an outer shell formed in hot pressed silicon nitride and having substantially uniform thickness in a direction parallel to the axis about which the rotor is rotatable and a heat resistant insert which can be either graphite or reaction sintered silicon nitride which fills the space within the shell and is attached to the shell. A row of blades which can be either hot pressed or reaction sintered silicon nitride can be attached to the periphery of the rotor by diffusion bonding.

Abstract: The invention is concerned with apparatus for manufacturing gas turbine engine components e.g. guide vanes and blades, in dense silicon nitride starting with silicon nitride in a powder form.Guide vanes are usually in the form of an aerofoil portion and two shroud portions and according to the invention, the aerofoil portion is made in a first mould by hot pressing a mixture of silicon nitride powder and a fluxing agent, such as magnesia. The formed aerofoil is placed in a second mould so that each end extends partly into a space which is to be filled with a further mixture of silicon nitride powder and a fluxing agent. The further mixtures are hot pressed both to form the shroud portions and to amalgamate the shroud portions with the aerofoil portion.Features, such as, flanges and webs can be formed in the shrouds during the moulding process or they can be machined into the shrouds after the vane is removed from the second mould.