Dissimilar metal welds for pressure applications are widely used. Two different types of steel are welded for the use of superheater applications. To prevent carbon migration from the steel with low Cr content to high Cr content a nickel-based filler metal was used, NiCr20Mn3Nb. Due to differences in properties in the base materials a buttering is used on the martensitic steel with the same filler metal and different thermal combinations of preheating (20°C and 250°C) and post-weld heat treatment (20°C and 760°C). Hardness testing was performed to analyze the effect of these two variables. Vickers hardness testing, HV10, was performed through different weld zones, weld metal, heat-affected zone (HAZ) and base metals. The paper aims to determine which combination of thermal conditions for creation of dissimilar metal welds has hardness distribution within acceptable range through the dissimilar metal weld.