Excessive wear and leakage was discovered on three nickel cemented tungsten carbide (WC) pump seals. Visual examination identified gouges in the seal surfaces that were responsible for the leaks, along with widespread mineral debris throughout.
Analysis of the debris indicated that active corrosion was occurring in stainless steel, brass and aluminum components of the closed system. Also found were elevated levels of aggressive fluoride salts suggesting untreated municipal water was used as makeup water.
Precipitation of abrasive silicon and aluminum oxides introduced fine abrasive particles into the system, preferentially abrading the soft nickel matrix of the cemented tungsten carbide pump seal, releasing tungsten carbide particles that further accelerated abrasive wear. What is seen above is a high magnification SEM image showing typical 2-phase microstructure of nickel cemented tungsten carbide.