Thank you for investigation. But it is too fast to say about hardness or heat treatmet. Because this sleeve contain Al liquid with temperature 650-700 deg.C. Do you know tempering temperature of this piece when it was hardening? I am sure with this required hardness at 49-51HRc , tempering temp must be lower than 600deg.C. Once sleeve was worked under temperature more than tempering temperature for long time, its hardness possibly to be reduced.
I suspect with the surface treatment process(Nitriding). How hard? How depth? What process?
What will we do next? Send defective piece to Gloria? Please coordinate with K. Jo.