Couple of points. The sear may be low carbon steel and not harden at all or it may be plain medium carbon steel and will harden. If it will harden at all, you probably should quench in water. There will be no benefit to holding it at temper temperature longer than needed for it to heat all the way through. If it doesn't harden, then you will want to case harden it - Kasnit is a common hardening medium.

DDA