The Damage of a Plunger Operating in Carbamide Environment

The surface of plungers, operating in demanding conditions, is exposed to the effects of pumped media, which may be chemically aggressive, in combination with mechanical wear caused by the interaction between the plunger, the counterpart and possibly the solid particles included in the pumped media. To increase of plunger’s lifetime, their surfaces can be protected by different technologies of a surface treatment. One of them is the progressive technology of thermal spraying. A wide range of sprayed materials is one of the reasons for using these versatile coatings as the protection against corrosion, wear or high temperature exposition in order to increase the parts lifetime, reliability and safety. In this case, the TAFA Praxair JP-5000 spraying equipment was used for the creation of the WC-based hardmetal coating on the plungers operating in carbamide environment. Even though the spraying process and the check sample were without any sign of defects the plungers showed a critical damage after several hours of running. The damage mechanism, its possible causes and the proposed solution are discussed in this paper.