Method for the production of precision shapes

In a process for producing metal shapes from powder particles which includes the steps of shaping the particles into a self-sustaining porous preform, applying a porous coating to the preform, subjecting the coated preform to a vacuum whereby the preform is degasified, conducting a fusion step comprising heating the coated preform, while maintaining the vacuum, to a temperature sufficient to render the coating non-porous and pressure-tight, and subjecting the preform to hot isostatic pressing, the improvement wherein said coating is applied by forming a first barrier layer on the preform, said barrier layer comprising a composition sufficiently porous to permit said degasification and which remains solid during said fusion step, and applying a second layer over said first layer, said second layer comprising a metal alloy which is initially porous to permit said degasification, which fuses during said fusion step, and which is solid during the subsequent hot isostatic pressing whereby said second layer provides the means for rendering the coating non-porous and pressure-tight.