Structural features ensuring the increase of service characteristics of high-nickel steels for pressure vessels of prospective energy-generation reactors

Complex structure studies and mechanical tests of low carbon Ni–Cr–Mo–V steels with low and high nickel content (low-Ni and high-Ni steels) were performed. Mechanical tests showed that high-Ni steels in initial state are characterized by higher strength properties and lower values of critical temperature of brittleness in comparison with low-Ni steels. Estimation of input of various structural elements in ensuring yield strength and brittle fracture stress (which is connected with critical temperature of brittleness) was performed. It was shown that increased strength characteristics of high-Ni steels are determined mostly by higher density of nanoscale carbide precipitations and dislocations. It was also shown that lower critical temperature of brittleness of high-Ni steels is associated with lower width of substructural blocks and, consequently, with higher number of barriers to brittle transcrystalline crack propagation. •Investigations of structure and properties of steels with various Ni content were performed.•High-Ni steels have higher yield strength and lower critical temperature of brittleness.•Higher of yield strength is determined by higher density of carbides and dislocations.•Lower critical temperature of brittleness is determined by increased structure dispersity.