40CrNiMO :
The most common material is cheap, but when the temperature exceeds 250 degrees Celsius, the performance of the core shaft deteriorates significantly. The higher the temperature, the more severe the performance degradation.
17-4PH :
The most cost-effective, with better core performance than WR5, no temperature attenuation within 350 degrees Celsius, and constant torque.
In718 :
High quality nickel based alloy material with the best performance, but very expensive price.