Abstract
The work deals with investigation of influence of alloying elements (Mo, V), impurities (P), and hydrogen on sharp-notch strength and the failure characteristics of low-alloyed 2.6CrMoV steels at the temperature of -80 °C. After embrittling treatment, the steels show various failure modes, in dependence on both the P content and the content of the alloying elements. The sharp-notch strength of the steels increases and the area reduction decreases with alloying elements (Mo, V) addition. Phosphorus does not affect the sharp-notch strength essentially, but it affects the area reduction. The prior austenite grain boundary P-segregation causes an increase of the inter-granular fracture portion (IFP). It was confirmed that the Mo (up to 0.7%) influences beneficially the intergranular fracture resistance of the steels and the carbide particles formation at the prior austenite grain boundaries during tempering is caused by its increase up to (0.95%) during tempering. The vanadium influence on the failure mode of the investigated steels was manifested by the decrease of the inclination to hydrogen embritt-lement. Both the carbides formation and impurity segregation leads to an intergranular fracture portion increase. The hydrogen absorbed by the samples causes an increase in the fractured stress, decrease of the material area reduction and increase of the intergranular fracture portion.

Key words
alloying elements (Mo, V), impurities (P), hydrogen, sharp-notch strength, failure characteristics, low-alloyed 2.6CrMoV steels, intergranular fracture resistance, inter-granular fracture portion (IFP)

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