Microstructure and Properties of the Nitrided Layer of Nodular Cast Iron

Abstract

The plunger pair is an important part of the plunger pump. It is required to have high wear resistance, self-lubrication, deformation resistance, and sufficient strength and rigidity because of the harsh application environment, thus ductile iron is a common material for large piston pumps because of its excellent overall performance. In order to improve the friction and wear performance of spheroidal graphite cast iron plungers, a nitride layer was prepared on the ductile iron QT600-3 by the ion nitriding technique. The morphology of the permeable layer was observed with a metallographic microscope, and its hardness, friction, and wear properties were analyzed using a Vickers hardness tester and a multifunctional material tester. The results of the article show that the hardness of the nitrided specimens is greatly improved, which is about twice the hardness of the matrix. The friction coefficient is found to be much lower than the friction coefficient of the matrix; the diameter of the wear scar is small, showing a moderate change compared with the matrix; and the performance is about four times. Therefore, the ion nitriding technique can significantly improve the friction and wear resistance of the pump plunger pair.