Keyword: «microhardness»

The article presents the results of studies of the mechanical properties of prototypes of hard-alloy drilling inserts with ultrafine additives of magnesium spinel. In the composition of the prototypes, the percentages of ultrafine additives of magnesium spinel varied from 0.1% to 1.0%. The formation of a homogeneous structure in the volume was revealed. The absence of conglomerates of ultrafine additive powders on the surface was revealed. The work aims to analyze the mechanical properties of prototype drill inserts made of tungsten-cobalt alloys, which differ in the content of an ultrafine additive. In work, the instruments of the Central Collective Use Center of the Federal Research Center of the Yankee Scientific Center of the Siberian Branch of the Russian Academy of Sciences and CJSC "DV – Technology" were used. It has been shown that adding ultrafine powder of magnesium spinel to the charge composition of the tungsten-cobalt matrix increases density and hardness.

In this paper, the processes of structure formation during gas-thermal electric arc metallization with powder wire are considered. The basic composition of the charge is nickel alloy PGSR-4. Niobium powders were selected as modifying additives, the content of which in the charge of powder wires is: 0.1%, 0.3%, 1% and 5% by weight. The influence of niobium content on carbide formation, on the ratio of structural components, on the formation of oxide phases, and the dispersion of the surfacing microstructure are shown. Tribological studies have shown that the wear of samples decreases by an order of magnitude, starting with the addition of 0.3% niobium. With a niobium content of 1% and 5% in the powder wire, the wear resistance remains high, but the mass losses of the samples and the counterbody are balanced, which is due to the grinding of the microstructure and an increase in the uniformity of micromechanical properties.

The paper studies welded joints of high-strength pipe steels in twin-arc automatic welding in a shielding gas. The microstructure, transverse and longitudinal macro- and microhardness distribution in various zones of welded joints are studied. Mechanical tests for static tension and impact toughness at low temperatures are carried out. The causes of heterogeneity and the degree of softening in the heat-affected zone are established. The principles of reducing microstructural and mechanical heterogeneity are formulated.

The article presents the results of studies of the composition, properties and structure of the bushing and pin of the rear spring of a truck operated in low-temperature climatic conditions of the North. The levels of hardness and microhardness of the hardened layer and the central part of the pin are determined. The surface profiles of worn parts before and after operation are shown.

Solving the urgent problems of finding reliable methods for the early detection of damage in metal products and improving the accuracy of predicting their fatigue durability requires a deep understanding of the material's structural changes at different loading stages. The method of statistical analysis of microhardness was used to study the structural inhomogeneity and damageability of three zones of the aluminum alloy AD33, which failed during operation in the North, characterized by different degrees of low-cycle fatigue development. It is shown that the failure of the alloy is preceded by progressive structural inhomogeneity and a deviation of the microhardness distribution from Gaussian. Quantitative characteristics for the critical state of the alloy before failure have been established: the coefficients of structural inhomogeneity, damage accumulation, and the reduced sampling frequency increase by 3–4 times with a catastrophic 26% decrease in the average microhardness value.