Lean Duplex Stainless Steel

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Macrographic aspect of the sleeve longitudinal section where the coating was applied in the external side (top of the figure). It is possible to see that the sleeve was manufactured by centrifugal casting, with elongated grains from the external side, and equiaxial grains close to the internal side (bottom of the figure). There is a weaved interface between the sleeve and the first layer of thermal spray coating, 1 mm thick; and a second layer of thermal spray coating, 0.2mm thick (almost imperceptible at this low magnification).
49
VIEW
ML00147 / Aug.2018
WC Layer Detached from a Cast Lean Duplex
M - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Cm - NaOH Electrolytic Etched MacroDf - Coating Layer

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ML00147 — WC Layer Detached from a Cast Lean DuplexM - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Micrography of a longitudinal section of the sleeve close to the external surface, evidencing a tugnsten carbide thermal spray layer, thickness about 0.2 mm, at the sleeve outer diameter (OD), black due to the etch (top of the figure). This WC layer was deposited over a stainless steel layer disposed in several layers, non etched.
42
VIEW
ML00147 / Aug.2018
WC Layer Detached from a Cast Lean Duplex
M - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Cm - NaOH Electrolytic Etched MicroDf - Thermal Spray Layer
Micrographic detail of the interface between the two thermal spray layers, the first one in stainless steel (bottom of the figure) and the second one, at the surface,in tungsten carbide (top of the figure). The micrographic sample is etched and that is why the WC is dark (black) and the stainless steel is light (non etched).
41
VIEW
ML00147 / Aug.2018
WC Layer Detached from a Cast Lean Duplex
M - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Cm - NaOH Electrolytic Etched MicroDf - Thermal Spray Layer
Micrographic detail by scanning electron microscopy of the interface between the two thermal spray layers, the first one in stainless steel (bottom of the figure) and the second one, at the surface,in tungsten carbide (top of the figure). The composition of the first layer is similar to the base metal (lean duplex) and the composition of the second layer is WC in a Co matrix.
16
VIEW
ML00147 / Aug.2018
WC Layer Detached from a Cast Lean Duplex
M - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Cm - Electrolytic Etch Micrography by SEMDf - Thermal Spray Layer
Micrographic detail of the first thermal spray layer, in stainless steel with the same composition of the base metal (lean duplex).
16
VIEW
ML00147 / Aug.2018
WC Layer Detached from a Cast Lean Duplex
M - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Cm - Electrolytic Etch Micrography by SEMDf - Thermal Spray Layer
Micrographic detail of the interface between the substrate and the first thermal spray layer. The substrate (bottom of the figure) shows a ferritic-austenitic microstructure and detrimental phases that look like sigma at the delta and gamma interface. The thermal spray layer (top of the figure) presents the non-etched stainless steel, disposed in layers, with oxides (gray) and voids (black). The substrate is deformed in a thin layer at the interface.
34
VIEW
ML00147 / Aug.2018
WC Layer Detached from a Cast Lean Duplex
M - Lean Duplex Stainless SteelP - Centrifugal CastingAp - ShipCd - Lack of Sealing
Cm - NaOH Electrolytic Etched MicroDf - Sigma

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