Tempering behavior of a semi-high speed steel containing nitrogen

The decomposition behavior of martensite and precipitation characteristics of carbonitrides during the tempering process of a low-alloy high-speed steel (semi-HSS) containing nitrogen were investigated by means of transmission electron microscopy, scanning electron microscopy, energy dispersive spectrometry and electron energy loss spectroscopy. The results shown the secondary hardening effect is reinforced with addition of nitrogen and the secondary hardening temperature range has expanded. The stability of retained austenite is also studied. When tempered in the temperature range of 425–525 °C, large quantities of fine-scale V-rich nitride precipitations distribute in the matrix homogeneously. A complex carbonitride phase can form when tempered at 550 °C.