You are trying to drill a 25mm dia hole through this HRSA material. I visit Special Metals every couple of weeks and we supply 75% of their cutting tools (sandvik).
Consider the cost of a solid carbide drill around 25mm, this will not be cheap. U-Drill is a copyrighted Sandvik drill, all other indexable insert drills are just that and not U-Drills.
For small quantities s/c maybe the answer certainly with thru-coolant. Run around 25 M/Min Vc with a feed of around 0.08mm/rev
Use a U-Drill or the new CoroDrill 880 for larger quantities.