The rods description says solid tungsten carbide rod is an excellent material to process as HSS cutting tools and holemaking tools. That is the substitution the mill is willing to put in writing.
HSS still wins on toughness and price for short runs and interrupted cuts that shock a brittle edge. Carbide wins when the same flute geometry has to hold size across a batch of mold steel or abrasive composite.
No hardness-conversion chart is published on the source site, so none appears here. Pick a published grade from the rods table instead of asking us to invent one.