Phase-structure formation and features of the behavior of iron–high-carbon ferrochrome–nickel boride powder materials under abrasive wear conditions

Abstract

The study covers the effect of nickel boride (Ni 3 B) additives on phase-structure formation, physical and mechanical properties and resistance of iron – high-carbon ferrochrome powder (35 wt.%) to abrasive wear. It was found that Ni 3 B additives provide the formation of a multiphase, microheterogeneous structure of a matrix-filled material consisting of chromium steel and solid inclusions of complex chromium-iron carbides such as Ме 3 С, Me 7 C 3 and Me 23 C 6 and borides FeB, Fe 2 B that significantly increase the microhardness of solid phases from 8.34 to 11.65 GPa. It was also revealed that the increase in the content of a doping additive from 3.5 to 8.7 wt.% increases base material resistance to abrasion wear from 6.9 to 12.2 km/mm and decreases hardness from 75 to 68 HRA and bending strength from 1560 to 844 MPa. The method of optical profilometry was used to study the topographical features of worn surface morphology to estimate the depth and local development of wear on sample surfaces with standardized roughness parameters calculated based on 2D or 3D profiles. Average roughness parameters for each composition were found to be R a = 0.44÷0.6, R z = 0.49÷1.2 μm, and R p = 0.26÷0.56 μm for materials doped with Ni 3 B, and R a = 1.860 μm, R z = 0.813 μm, R p = 3.356 μm for the base material. It was shown that the promising compositions that combine acceptable physical and mechanical properties and improved abrasive wear resistance are materials based on the Fe–35%FeН800 system containing 5.2–6.9 wt.% of Ni 3 B.