Hardening during tempering of steels rich in molybdenum, tungsten, vanadium or chromium, such as high-speed and hot-work tool steels. Around 500 to 600 °C very fine alloy carbides precipitate and retained austenite transforms on cooling, so hardness climbs to a second peak instead of falling. Tools tempered at or just above that peak hold their hardness when cutting edges and die faces run hot.
Temper the H13 past the secondary hardening peak, around 1,100, or the die checks early.
Also heard as
- secondary hardness peak
Related terms
Double tempering
Tempering a part twice, cooling to room temperature in between, to temper martensite formed after the first.
Carbide
Any hard compound of carbon with iron or alloying elements such as chromium, vanadium, molybdenum or tungsten.
Tempering
Reheating hardened steel below its lower critical temperature to trade some hardness for toughness.
Retained austenite
Austenite that fails to transform during the quench and survives at room temperature inside hardened steel.