304 stainless steel brazing incorporating tungsten nanoparticles

Metallurgical Interaction among BNi-9 and Waspaloy, FSX-414 or 304-Type Stainless Steel under TLP Cycle

“…The solidification microstructure of the MZ was formed at a higher cooling rate compared to the isothermally solidified metal, so it is easier to contrast them, see Figure 7. The MZ [18] has been referred to by other authors as the Athermal Solidification Zone [8,12,39,40], or interlayer [41]. The thickness of the MZ increases when the gap between the plates is augmented, as previously reported by Cook [42].…”

“…In general, the treatment temperatures are in the 1065-1225 • C range, a vacuum of approximately 1.33 × 10 −3 Pa is applied, and most of the thickness gaps are in the 20-200 µm range. Argon atmospheres have also been used [15,18,19]. Wu et al [22] used 5% hydrogen and 95% Ar for wide gap brazing.…”

“…This phenomenon occurs when the initial gap thickness overcomes the isothermal solidified layer. This eutectic constituent is composed of a Ni-based solution and Ni and Cr Borides [10][11][12][13]18,33]. The morphology and distribution of the eutectic constituent could be changed by nanoparticle additions, as observed by Hernandez et al [15,18,19].…”

“…These authors studied the effect of Si or W nanoparticles added to BNi-9. The filler metal with Si nanoparticles was applied to 304-SS [19], while the effect of W nanoparticles addition was studied in 304-SS [18] or Inconel 725 [15].…”

“…In these later materials, it is observed in the PZ that small precipitates are concentrated in a narrow zone close to the base metal, BM, then the precipitates become larger and coexist with a film constituent, and finally become scarce until they disappear. The PZ [18,44] has been referred to by other authors as the Diffusion Affected Zone [8,12,13,16,21,40,45,46].…”