Creep Resistance and Structure of 10% Cr–3% Сo–2% W–0.29% Cu–0.17% Re Steel with Low Nitrogen and High Boron Contents for Unit Components of Coal Power Plants
IF 1.8 4区 材料科学Q2 MATERIALS SCIENCE, CHARACTERIZATION & TESTING
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Abstract
The creep resistance and structure of 10% Cr–3% Сo–2% W–0.29% Cu–0.17% Re steel with 0.1% carbon, low nitrogen content and high boron content were investigated by creep rupture testing at a temperature of 650°C and stresses from 200 to 100 MPa applied in 20-MPa increments. For comparison, 9% Cr steel with 0.1% carbon, 0.05% nitrogen, and 0.005% boron was considered. The steels were subjected to preliminary heat treatment including normalizing at 1050°C for 1 hour, tempering at 750–770°C for 3 hours, and cooling in air. The structures of both heat-treated steels exhibited martensite laths with boundaries pinned by М23С6 carbides, and the rearrangement of dislocations was retarded by MX particles. A significant difference between 10% Cr and 9% Cr steels was the presence of fine М23С6 carbide particles characterized by orientational relationships with the ferrite matrix and MX carbonitrides, whose volume fraction was 6 times lower. Short-term tensile tests at room temperature showed no differences between the steels, while the creep rupture strength of 10% Cr steel was 13% higher than for 9% Cr steel. The creep deformation mechanism of the steels was also different. Structural analysis of 10% Cr steel after creep tests revealed no substantial changes in its lath structure: the lath width increased by only 58% and the dislocation density was reduced by a factor of 2. Comparison with 9% Cr steel showed that the good structural stability of 10% Cr steel during creep is caused by the high coarsening resistance of second phase particles, whose coarsening rate is 1-2 orders of magnitude lower than that in 9% Cr steel.
期刊介绍:
The journal provides an international medium for the publication of theoretical and experimental studies and reviews related in the physical mesomechanics and also solid-state physics, mechanics, materials science, geodynamics, non-destructive testing and in a large number of other fields where the physical mesomechanics may be used extensively. Papers dealing with the processing, characterization, structure and physical properties and computational aspects of the mesomechanics of heterogeneous media, fracture mesomechanics, physical mesomechanics of materials, mesomechanics applications for geodynamics and tectonics, mesomechanics of smart materials and materials for electronics, non-destructive testing are viewed as suitable for publication.