The PRCI hardness model is the predicted Vickers hardness of the weld HAZ using a 10-kg load. The hardness curve is based on the Yurioka equations which are based on Vickers hardness with a 10-kg load.
Is it possible to change the vickers hardness result from PRCI to the equivalent of 5 kgf load?
Below is a reference that talks about a method to convert the same hardness measurement type made at different loads.