Influence of hydrogen on the long-term strength of tire steels

We establish that the time to fracture of specimens made of 8Mn−8Ni−4Cr steel decreases in tap water at high stresses by a factor of 2.5 and, in the course of electrolytic hydrogenation, by a factor of 35–50 as compared with that obtained in tests in twice-distilled water. The use of a hardening surface treatment and protective coatings under the same conditions increases the long-term strength by a factor of 1.5–2. A combined plasma Al+V₂O₅ coating with subsequent soaking with epoxy compound preserves the plastic characteristics of steel and, hence, increases the time to fracture in the best way. The application of plasma nitride (TiN+CrN+NbN) coatings on the thread and mounting surfaces of elements of a rotor shroud unit gives them a high hardness and resistance to dripping and scoring and prevents the penetration of hydrogen-containing media into the base. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 4, pp. 37–42, July–August, 1999.