For seal-free pistons in the pharmaceutical, medical technology or food processing industries, designers want stainless steel components that are resistant to scratches and corrosion. But how do you harden a stainless steel by carburizing the austenite matrix? For the necessary corrosion resistance, the chromium concentration - even locally - must not be reduced; the formation of CrCx must be prevented. The GWP has developed a simple low-temperature process for this purpose. The cut shows a hardening zone with very small diamond indentations compared to the base material.