To reduce the susceptibility of the alloys to the
precipitation of M6C, μ phase, and P phase, steps
are taken during melting to minimize their carbon
and silicon contents, silicon being a known
promoter of intermetallic phases, such as μ. As to
the effects of these second-phase precipitates on
the properties of the C-type alloys, it is well
known that the heterogeneous precipitates that
occur at temperatures in excess of 650 °C (1200
°F) are detrimental to both corrosion resistance
and material ductility. On the other hand, the
homogeneous precipitation reaction that occurs
at lower temperatures can be used to strengthen
the C-type alloys while maintaining good ductility
(Ref 14). Indeed, a Ni-Cr-Mo composition
(C-22HS alloy) that can be strengthened by this
mechanism in a short period of time (48 h) has
been developed