I know of one Aerospace prime that deviates from the AMS 2431 documents by stating the hardness of conditioned cut wire shall be 45HRC minimum. While on one hand it gives the shot peener a wider range of material to choose from, this could lead to problems. The hardness range selected for the machine/process should be frozen. Example: If you add harder media to your machine that was using a softer media it will cause havoc with your ability to repeat the process from your originally developed saturation curves.
The upfront cost of high hardness conditioned cut wire is true. One should consider the potential energy savings long term. A high hardness media will achieve the same intensity value with less air pressure / wheel speed.
