and heated to a temperature between 1600 u00b0 f and 2300 u00b0 f where the coated metal powders are easily deformable under pressure for most materials the furnace atmosphere should be either inert or reducing to prevent oxidation of the powder such a furnace is indicated at 18 and it may contain inert gas such as argon or nitrogen referring to fig2 the next step in the process is to place the liner containing the green now lightly sintered layer 11a within a step die 19 where the liner fits into the large cavity i e first chamber 19 in the die as shown in the figure and having inner cylindrical walls 19a and 19b the die second chamber 20 throat diameter d 1 should be equal to or smaller than the 34 green 34 internal diameter d 2 of the mud pump liner 11a this assures relatively shearless pressing of the green powder metal cladding 11a under largely lateral pressure during the pressurizing step chamber 20 has a bore 20a as seen in fig3 pressurization takes place in a press 21 after filling both the die and the pump liner cavities with a refractory powder 22 already at a temperature.