Fiat Societa Per Azioni

Pier C Martinengo

Angelo Giachello

Giuseppe Tommasini

Paul Popper

Carlo Carughi

Sintered silicon nitride articles are prepared by sintering a silicon nitride compact of a density of at least 1.3 g/cm.sup.3 in nitrogen gas atmosphere at substantially atmospheric pressure, while the compact is embedded in a protective powder comprising silicon nitride, boron nitride, or a mixture of silicon nitride and boron nitride, and one or more sinterization additives for silicon nitride, said additives being present in the protective powder in an amount of from 3 to 20% by weight.

Process for sintering silicon nitride compacts

A process for forming a protective metal diffusion coating on a metal or metal alloy workpiece including internal cavity surfaces, comprises coating the workpiece with a slurry in acetone and cellulose acetate of a powder of average grain size of 0.5.mu. to 10.mu., including aluminum and possibly chromium and/or a small quantity of cerium or yttrium hydride and heating the workpiece in a non-oxidizing environment to dissociate the hydride and effect diffusion of the metals into the surface of the workpiece.

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Turin, Italy

Pier C Martinengo