Chemical method of fatigue and corrosion fatigue crack growth arrest in steels by metal treatment with the special technological environment


Novel method of fatigue crack growth arrest in structural steels based on artificial creation of crack closure effect is proposed. Special technological environment is used which, falling into a crack cavity, forms solid products there. These products practically totally fill up a crack cavity and serve as a wedge which prevents crack closure during a period of unloading and, respectively, cyclic deformation in a crack tip. Fatigue crack growth curves are built for low alloyed steel without and with crack treatment which demonstrate crack arrest in a wide range of stress intensity factor (SIF) ΔK, from the threshold level up to almost fatigue fracture toughness Kfc. i.e for the whole actual range of ΔK. The peculiarity of artificial crack closure is accentuated: a decrease of effective ΔK is accompanied by an increase of a middle level of SIF therefore a risk of stress corrosion cracking and corrosion fatigue rises. This factor is especially important for long-term operated steels which lost their initial brittle fracture resistance. The interaction of active components of the technological environment with a metal at the crack surface which provides formation of solid products in a crack cavity is analyzed. Some technological aspects for practical application of the proposed method are considered.

Countries: Ukraine

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