PSI - Issue 40

M.V. Fedorov et al. / Procedia Structural Integrity 40 (2022) 145–152 Fedorov M.V., Vasilieva M.I. / Structural Integrity Procedia 00 (2022) 000 – 000

146

2

Nomenclature UDP

ultradispersed spinel powder layered double hydroxides

LDH

XRD X-ray diffraction

1. Introduction. Hard-facing alloys are widely used in the industry for processing new alloys with high hardness due to their unique properties. At the same time, for example, the wear resistance of hard alloys is much higher than the wear resistance of more accessible high-speed steels. The strength of hard alloys is significantly lower than the strength of more accessible high-speed steel. This property of hard alloys is due to their well-known brittleness and low ductility, which leads to their low resistance to tensile, bending and impact stresses. Today, according to Byakova et al. (1993), Samotugin et al. (2007) and Loktev (2005) many surfaces and volumetric hardening methods of hard alloy materials, such as modification, alloying, etc. In addition, one of the ways to improve the resistance to wear and shock-abrasive loads and reduce the brittleness of carbide materials is the development of new compositions with additives. The additives play the role of inhibitors of the growth of carbide grains, which are the skeleton in the structure of the hard-alloy material. Thus, the introduction of the additive into the composition of hard alloy materials affects their structure formation and, accordingly, directly affects the material's final physical and mechanical properties. Refractory metals, carbides, oxides, nitrides are used as additives. According to Gorshkov et al. (1988), Braulio et al. (2011), Fajkov (2007), Mazzonia et al. (2002), Nakagawa et al. (1995) one of these additives is an ultradispersed powder of spinel. Many works describe the role of spinel as a grain growth inhibitor, but there are still questions about the mechanism that inhibits grain growth during sintering. Thus, in this work, we have studied processes that occur during sintering in UDP spinel at a sintering temperature of 1450 ○ C. 2. Statement of the problem and methods of solution. Approximately 8 mg (precise band-and-hook hinge) of UDP was prepared. Because the UDP spinel can absorb moisture and impurities, it is necessary to determine and identify the elements of the new composition and phases with physically or chemically bound moisture. This task was solved using X-ray microspectral and X-ray phase analysis. In order to identify phase transitions, thermal analysis was carried out in the following modes: from room temperature to 600 ○ C; 1000 ○ C and 1450 ○ C. After each mode, X-ray phase analyses of heated powders were carried out to establish the presence of the appearance of new phases. 3. Materials and methods. The object of research was ultradispersed spinel powder (MgAl 2 O 4 ). Elemental chemical composition of the powder (wt.%): MgO was 28.2 and Аl 2 О 3 was 71.8. The spinel structure consists of a three-layer densest packing of oxygen atoms, and Betextin (1950) described other structural features. UDP of magnesium-aluminium spinel MgAl 2 O 4 was produced at the ISSCM SB RAS. Structural characteristics of the powder: the external view in the form of a fine white powder; by the content of impurities, the powder corresponds to the type "pure"; the microstrains is 0.60 %; the specific surface area is 72.43 m 2 /g; the size of primary particles (crystallites) is 10.8 nm; the density is 3.55 g/cm 3 . The research methods were used, such as the X-ray microanalysis to determine the quantitative composition, the X-ray phase analysis for phase identification and the thermal analysis to study processes affecting the properties of materials under the influence of temperature. The X-ray microanalysis was performed using a scanning electron microscope JSM-6840LV (JEOL Ltd., Tokyo, Japan) with an Energy 350 Oxford Instruments energy dispersive spectrometer. The X-ray phase analysis was performed on a diffractometer PHASER D2 (Bruker, Ettlingen, Germany); the PDF-2 / Release 2011 RDB database was used to identify minerals. The thermal analysis was