Bm. Korevaar et al., Effects of nitriding on fatigue strength of quenched and tempered steel: role of interstitial nitrogen, MATER SCI T, 17(1), 2001, pp. 54-62
This paper describes an investigation into the effects of nitriding, denitr
iding, and renitriding, on the rotating bending fatigue strength of notched
specimens of the quenched and tempered steels 24CrMo13 and 42CrMo4. The ef
fects of the different treatments were characterised by microstructural inv
estigation, hardness measurements, determination of the nitrogen and carbon
contents in the diffusion layer, and determination of surface macrostresse
s. Nitriding induced a doubling of the fatigue limit. Denitriding only part
ly removed the effect of the nitriding treatment, because the strength incr
ease caused by precipitation of alloying element nitrides remained unchange
d, and only the effect of interstitially solved nitrogen disappeared. For n
itrided and renitrided specimens an approximately linear relationship was f
ound between the surface hardness and the fatigue strength, Denitriding cau
sed a larger decrease in the fatigue strength than could be explained by th
e loss of surface hardness, The change in macrostresses from compressive to
tensile also played a part. The role of interstitially dissolved nitrogen
in determining the fatigue strength was found to be larger than assumed thu
s far. MST/4598.