Precipitate phases in type 321 stainless steel after aging 17 years at ∼600°C

Electron beam freeforming of stainless steel using solid wire feed

“…Previous work on 321 and 347 stainless steels has indicated considerable miscibility between the MC carbides (TiC, NbC, ZrC, HfC, VC and TaC) due to the sub-stoichiometric characteristics of the precipitates, which thus explains the interlacement of the niobium and titanium within the particles formed in the build-up [16]. In addition, the presence of MC carbides in stabilized steels, even for very low carbon contents, show two types of distribution: (i) a coarse dispersion, 1-10 lm in size, of primary particles formed during solidification; and (ii) a fine dispersion, 5-500 nm in size, of secondary precipitates [15,[17][18][19], which support the range of particle sizes (0.3-7 lm) observed in the present work for the Ti (C, N), (Nb, Ti) carbonitride complexes and Nb (C, N) precipitates.…”

Investigation of the effect of the types and densities of grain boundary carbides on grain boundary cavitation resistance of AISI 321 stainless steel under creep–fatigue interaction

“…This alloy is used mainly in superheater tubing in conventional coal-fired boilers, as well as in a number of other critical applications such as guide tubes, pipes, and pressure vessels in gas-cooled nuclear reactors. The addition of Ti prevents the formation of chromium-rich carbide precipitation at the grain boundaries which are known to be deleterious to the creep life of the material [4][5][6][7][8].…”

Effects of TiC and Cr<SUB>23</SUB>C<SUB>6</SUB> Carbides on Creep-Fatigue Properties in AISI 321 Stainless Steel

“…For Cr 23 C 6 carbide precipitation heat treatment of (1) process is applied and for TiC carbide (2) process is conducted. When TiC and Cr 23 C 6 have the same size and density at the grain boundary, different lattice parameters of the carbides could affect mechanical properties of the alloys. After solid solution treatment for TiC carbide precipitation, the alloy was furnace-cooled to obtain the similar size and density of TiC at grain boundaries compared with those of Cr 23 C 6 obtained by the (1) process.…”

“…Second, if TiC carbides are presented as a fine dispersion in matrices and grain boundaries, they improve tensile and creep strength significantly at both high and low temperatures. [4][5][6][7][8][9] Generally, the carbide at grain boundaries provides the preferential site for the cavity nucleation under creep-fatigue interaction conditions. [10][11][12][13][14][15][16] The higher the carbide density at grain boundaries, the shorter creep-fatigue life of materials.…”