Effect of microstructures on corrosion and erosion of an alloy steel gear pump

• Studied effect of microstructures on corrosion and erosion behavior of alloy steel gear pump.
• The pump was suffered from corrosion.
• Localized galvanic cells formed between M23C6 carbides and martensite matrix.
• Microstructures are the controlling factor of corrosion of the alloy steel pump.

Investigation on an alloy steel gear-pump has been carried out to understand the effect of microstructures on corrosion and erosion behavior of the material. The alloy tool steel gear pump was designed to replace an existing pump made of grey cast iron to increase the service life to 7–8 years from 4–5 years. However, the new pump, used for dispensing hot adhesive polymer at 170 °C and 8 bar pressure, was damaged due to pitting corrosion within one year of service. Local galvanic cells were formed between M23C6 carbides and martensite matrix of steel plate of the pump in presence of sulfide ions sourced from liquid adhesive followed by anodic dissolution of martensitic matrix surrounding the carbides. As a consequence, hard carbide particles were dislodged and facilitated the pump to undergo wear rapidly.

Localized galvanic cells formed between M23C6 carbides and martensite matrix. The anodic dissolution of martensitic matrix in presence of sulfide ions sourced from the liquid adhesive medium caused carbides dislodging and facilitate the pump to undergo wear.Figure optionsDownload as PowerPoint slide