Ferritic transformation of an austenitic stainless steel by hot dipping in liquid tin or tin-nickel alloys

Dissimilar Metal Solution from Solid Alloys as Observed for Steels and Nickel‐Based Alloys in the Presence of Lead‐Based Liquid Alloys or Liquid Tin

“…The habitus of ferrite changes from globular to columnar under conditions hampering the removal of Ni, i.e., after pre-saturation of the liquid with Ni, for a comparatively small volume of liquid or decreasing temperature. 20 At > 1050°C, the depletion zone shows prominent surface recession, and the ferrite tends to recrystallize into a continuous layer. Additionally, Sn diffuses into the austenite grain boundaries, with a preference for twins in the austenitic structure, triggering local austenite/ferrite transitions inside the steel.…”

“…Additionally, Sn diffuses into the austenite grain boundaries, with a preference for twins in the austenitic structure, triggering local austenite/ferrite transitions inside the steel. 20 In the case of Ni-based alloys, the highly soluble constituents include the parent element of the alloy (Ni), suggesting that the percolation mechanism 26,27 is likely to operate. This is reflected by the innermost part of the depletion zone that forms in Alloy 2.4663 (Ni-22Cr-12Co-9Mo) during the exposure to liquid Sn at 700°C (Fig.…”

“…22 The columnar Cr-Mo is reminiscent of the ferrite structure attributed to relatively low velocity of Ni transfer to the bulk of the liquid metal. 20 Obviously, at temperature higher by 300°C, improved lattice and surface diffusion renders interconnection of the atoms of the highly soluble elements in the alloy less important for selective leaching to proceed at the maximum possible rate. Additionally, the capacity of the liquid for taking up Ni as well as other alloying elements is naturally higher.…”

“…The influence of oxygen dissolved in the liquid metal as well as the formation of intermetallic compounds is discussed. The observations evaluated with respect to dissimilar metal solution stem from experiments in Pb-based alloys 1,3,[8][9][10][11][12][13][14][15][16][17][18][19] and liquid Sn [20][21][22][23] at 400-750 and 500-1000°C, respectively.…”

Fundamental Interactions of Steels and Nickel‐based Alloys with Lead‐based Liquid Alloys or Liquid Tin

“…Austenitic steel exposed to liquid Sn [20] shows ferrite formation only at >650 °C and most notably at >840 °C. Both Cr in the steel and Sn stabilise the ferritc phase that is still observed at >1050 °C.…”