On effect of rhenium on mechanical properties of a high-Cr creepresistant steel

Addition of 0.2% rhenium in the experimental steel improved the short-term creep strength at 650 C. Comparison of kinetics of tungsten depletion from the matrix in different high-Cr martensitic steels showed that rhenium in the experimental 10Cr-3Co-3W-0.2Re steel did not lead to retaining an increased amount of solute W in the ferritic matrix during both aging and creep at 650 C. At the same time, the precipitation of the high fraction of the fine Laves phase particles provided the effective particle strengthenin

Strain-induced Z-phase formation in a 9% Cr-3% Co martensitic steel during creep at elevated temperature

The size and distribution of Cr(V,Nb)N (Z-phase) particles in a 9Cr-3Co-2W-0.6Mo-0.1Ni-0.2V-0.06Nb-0.1C-0.05N-0.005B steel subjected to creep rupture test during 11,151 h at 650 °C under an applied stress of 100 MPa were studied. The replacement of V-rich (V,Nb)(C,N) carbonitrides by Z-phase was accelerated by plastic flow as suggested by a comparative analysis of these particles in different portions of crept specimen, namely, the grip section, the portion of uniform elongation, and the necked portion

Structural evolution of P92-type martensitic steel during creep at 650 C

Microstructure and a dispersion of secondary phase particles were examined in P92-type steel after creep test at temperature of 650 ◦C and an applied stress of 80 MPa in grip, gauge and necked portions of specimens. The structural changes in the gauge and necked sections were characterized by transformation of the tempered martensite lath structure into relatively coarse subgrain one accompanied by the coarsening of M23C6 carbides and precipitation of the Laves phase. No significant effect of creep strain on particle coarsening was foun

Nucleation of W-rich carbides and Laves phase in a Re-containing 10% Cr steel during creep at 650 °C

The nucleation of the Laves phase particles in a Re-containing 10% wt. Cr-3% Co-3% W steel with a low nitrogen and a high boron contents during creep is characterized by distinctive features. The precipitation process can be written as M23C6 carbide → M6C carbide → Laves phase. The nucleation of all phases in this precipitation sequence is heterogeneous. The M23C6 carbides precipitate on the boundaries of martensitic structure during tempering at temperature of 770 °C. The M6C (Fe3W3C) carbides precipitate during both tempering at 770 °C and creep at 650 °C on the M23C6/ferrite surfaces and on the martensitic lath boundaries. The M6C carbides have the mutual relationship of crystal orientations with both the M23C6 carbides and ferrite. The chemical composition of the M6C carbides depends on their nucleation site

Effect of tantalum on the tensile properties of 12%Cr martensitic steels for steam blades

Co-modified 12%Cr martensitic steels are perspective materials for steam blades for fossil power plants which are able to work at ultra-supercritical parameters of steam (T=620-650°C, P=2530 MPa

Coarsening of Laves phase and creep behaviour of a Re-containing 10% Cr-3% Co-3% W steel

The coarsening of Laves phase in a Re-containing 10% Cr-3% Co-3% W steel during both creep and ageing at 923 K was investigated. The depletion of W solutes from the ferrite matrix is accompanied with the precipitation of Laves phase, wherein creep strain accelerates both these processes. The equilibrium W content in the ferritic matrix of 1.24 wt% and the volume fraction of Laves phase of 1.6% is reached after 500 h of creep and 1000 h of agein

Superior creep resistance of a high-Cr steel with Re additives

Re-containing 10Cr-3Co-3W martensitic steel with low nitrogen and high boron contents exhibited a rupture time of 10,987 h at 650 C/140 MPa. This superior creep resistance was caused by partially saved tempered martensite lath structure due to precipitation of M₂₃C₆ carbides and Laves phase chains on lath boundaries as well as their high resistance to coarsening.M₂₃C₆ carbides were characterized by decreased interfacial energy that resulted in the retention of the orientation relationship between M₂₃C₆ carbides and ferritic matrix. Re slowed down diffusion of W, Mo and Cr atom

Analysis of mechanical properties for the heat resistant CO-modified 12 and 9% CR steels

An analysis of mechanical properties has been performed for 12% Cr and 9% Cr steels by means of tension tests at 20 and 650°C and yield tests at 650°C and applied stresses of 200-100 MPa with a step of 20 MPa. The yield strength and ultimate tensile strength of the 12% Cr steel are, correspondingly, 614 and 710 MPa at 20°С and 365 and 390 MPa at 650°

The effect of creep and long annealing conditions on the formation of the Z-phase particles

The influence of the temperature, applied stress, degree of creep deformation, and aging time on the formation of Z-phase (CrVN) particles in 9% Cr 10Kh9K3V2MFBR martensitic steel at temperatures of 650 and 675°С upon long aging is studied in this wor