Wear Resistance of Hardened Nanocrystalline Structures in the Course of Friction of Steel-Grey Cast Iron Pair in Oil-Abrasive Medium

Abstract

The results of the research studying the influence of modified hardened surface layer after friction hardening on wear resistance in the course of oil-abrasive wear of steel-grey cast iron friction pairs are presented. Friction hardening is one of the surface hardening methods with the use of highly concentrated energy sources. A nanocrystalline hardened (white) layer is formed in the surface layers after the friction hardening. The thickness and microhardness of the hardened layer depends on carbon content in the steel and its preliminary heat treatment. Thus, thickness of the hardened layer was 120 µm, and microhardness was 5.6 GPa, with the initial structure hardness of 3.2 GPa, in hardened and high-tempered test-pieces of Steel C45 (EN) after the friction hardening. 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 performance of the pair “Steel 41Cr4 (EN)-Grey cast iron EN-GJL-200” during sliding friction in oil-abrasive medium. When increasing the unit load area from 2 to 6 MPa, wear rate of the hardened pair decreased by 2.1–3.7 times in comparison with an unhardened pair. Only one component of the friction pair was hardened.