THE EFFECT OF NANOCRYSTALLINE LAYERS ON THE WEAR RESISTANCE OF GREY CAST IRON DURING FRICTION IN AN OIL-ABRASIVE MEDIUM

摘要

Friction hardening is one of the surface hardening methods with the use of highly concentrated energy sources. In the "tool-treated surface" contact area, the surface layer of a metal is heated at a very high rate to phase transition temperatures, and then it is cooled at a high rate, which results in the formation of hardened nanocrystalline layers. The studies carried out have shown that a hardened nanocrystalline layer is formed in the surface layer in the course of friction hardening of cast-iron (EN-GJL-200) components. The layer thickness is 90-120 μm, and the microhardness is 7-8 GPa. Grain size of the hardened surface layer was equal to 20-40 nm near the treated surface. It is shown that the hardened layer significantly increases the serviceability of the pair "grey cast iron-grey cast iron" during sliding friction in the lubricated-abrasive medium. When increasing the unit load from 2 to 6 MPa, the wear rate of the hardened pair decreased by 2.6-4.2 times in comparison with an unhardened pair. Only one component of the friction pair was hardened.