Metal to Metal Seating Design for HVAC Change-Over Manifold Valve,

[wetwilly17]

I've been asked to reverse engineer an obsolete valve for a one-off application. I've attached pictures of the cross-section of the original valve to illustrate the configuration. I am worried about not being able to achieve leak-tightness due to the metal to metal seating. Please help point me in the right direction: what are some tips in achieving leak tightness for this seat configuration? What are typical manufacturing tolerances? Materials?

I used an uncalibrated PMI gun to get an idea of the materials:
Valve Body (base material): 93.13% Fe, 2.41% Cu, 2.08% Al, 0.91% Mn, 0.38% Si, 0.30% Su, 0.2% Pb, 0.18% Cr, 0.17% Zn, 0.15% Ni, 0.08% Ph
Valve Stem (base material): 93.67% Fe, 3.68% Cu, 0.82% Mn, 0.48% Su, 0.43% Si, 0.31% Ti, 0.25% Pb, 0.21% Zn, 0.11% Ni, 0.03% Cr
Valve Stem (surface material/coating): 90.16% Fe, 4.98% Ti, 2.61% Cu, 0.79% Mn, 0.42% Si, 0.31% Zn, 0.3% Su, 0.25% Pb, 0.09% Ni, 0.07% Ph, 0.03% Cr

THANKS!

 

[btrueblood]

Make one side or the other (i.e. poppet or seat) an elastomer at the contact point, or soft plastic (PTFE comes to mind).