A stator vane with an endwall having a mate face with a seal slot, where the seal slot includes a row of feed slots on an outer side and two rows of impingement slots on an inner side and along the sides of the seal pin. Each impingement slot is connected by an impingement hole to one of the feed slots. With the seal pin secured within mate face seal slots of adjacent endwalls, cooling air flows through the feed holes and through the impingement holes to provide convection and impingement cooling for the mate faces. The spent impingement cooling air then flows out the diffusion slots and into the gap to purge hot gas flow away from the gap.