Hard Facing with Cobalt Base Alloy- Stellite--1

Primary Heat Transport (PHT) System Pumps are used for circulating Heavy Water at high temperature in the PHW Reactors. A pair of statioi^ry and rotary S.S. mechanical seals are used in these pumps. To provide sufficient weatf resistance, corrosion resistance and a variety of additional properties, the hard cobalt based alloys are faced on the mating surfaces of the pair of mechanical seals. Initially, Stellite-6 was hard faced on the seals. Since the seals were wearing out fast, the need for a much harder facing material, to extend the life of the mechanical seals, was felt. Hence, Stellite-1 was an obvious choice. Nevertheless it was not an easy task to replace Stellite- 6 with Stellite-1.