Nickel-molybdenum alloys, or B-type
alloys, are known for their excellent resistance
to nonoxidizing (reducing) media, such as
hydrochloric and sulfuric acids. The original B
alloy (N10001) was invented in the 1920s, and
it had a nominal composition of Ni-28Mo-5Fe-
0.3V, with a maximum carbon content of 0.05
wt% and a maximum silicon content of 1 wt%.
The alloy was used successfully for many years,
but it suffered an important drawback in that
fabricated components required a solution heat
treatment in order to avoid corrosion attack in
the weld HAZs. Experimental work from 1958
to 1960 indicated that the corrosion resistance
of the alloy could be significantly improved by
reducing the carbon, iron, and silicon levels
(Ref 4, 5). However, the achievement of very
low carbon levels on a production scale did not
occur until the invention of the argon-oxygen
decarburization (AOD) melting process (Ref 6).
This enabled the commercialization of an
improved nickel-molybdenum material, B-2
alloy (N10665), in the early 1970s (Ref 7).