Your guess is close. Nichroma is a stainless steel grade used for welding filler. It was manufactured by Lincoln Smitweld BV, and its nominal composition is C 0.025, Cr 20.0, Mn 0.8, Mo 2.3, Ni 9.5, and Si 1.0. This grade is typically used for welding dissimilar joints and repair welding. They also manufactured a grade called Nicromo, which is a Cr and Mo alloyed Ni-base electrode suitable for welding alloy 59, alloy C276, Cu and C22.