used to increase the coating thickness up to 10 of the particle radius and hence the alloy concentration in the finished p m products several layers of coatings 22 24 and 21 of different alloying elements e g ni cr mo for fe may also be applied onto the same base metal fe particles 22 24 21 to achieve multiple alloying results multiple alloying can also be achieved with a single but mixed solution containing the required alloying elements it is usually desirable to cover the entire surface of the base metal particles often covering a major i e over 50 of the particle surface is sufficient particularly when moo 3 wo 3 or mixed moo 3 wo 3 coatings are used followed by heating to melt and spread the compounds even if the coating does not completely cover the entire particle surface or spread thereon elemental interdiffusions during the sintering step effectively homogenize sufficiently the alloy composition to produce useful p m products notice that the inner metal particles are ductile while the outer coatings containing the compounds of the alloying elements are fragile and easily fractured of fragmented under deformation during the pressing or compressing step when the powder particles are compacted into powder compact the inner yieldable base metal particles yield and deform under the compacting pressure into a compact of higher packing density and less porosity than the powder pack before the pressing step simultaneously the surface coatings containing the alloying elements deform and fracture or fragment into tiny pieces to fill the nearly microscopic i e less than 0 1 mm voids between the pressed base metal.