PSI - Issue 65

E.G. Zemtsova et al. / Procedia Structural Integrity 65 (2024) 310–316

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E.G. Zemtsova et al. / Structural Integrity Procedia 00 (2024) 000–000

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1. Introduction

The observed increase in the strength of metal matrix composites is directly related to a decrease in the particle size of the reinforcing phase to several tens of nanometers. This is due to an increase in the specific area of interaction between the reinforcing phase grains and the matrix grains, a decrease in the size of material defects, which are simultaneously particles of the reinforcing phase (Kumaraswamy et al. (2021), Zemtsova et al. (2019)). Hardening of materials occurring at the same time is in good agreement with the mechanisms of Hall-Petch and Orovan. There are many computational works in which the effect of hardening in composite materials is theoretically justified. A number of authors agree that the active influence of the dispersed phase on the morphology, dispersion and distribution makes it possible to obtain a unique combination of properties that is unattainable even in alloys (Popov et al. (2005)). Also, the use of solid inclusions insoluble in metals as a reinforcing phase ensures the stability of the properties of the resulting material during its long-term operation. Carbides is the class of materials widely used as a reinforcing phase for the manufacture of Ni matrix composites. The popularity of carbides is due to their high hardness, which implements the hardening of the material by the Orovan mechanism (preventing the spread of dislocations), as well as the transfer of load to reinforcing particles. Ni composites can be reinforced with carbides of tungsten, silicon, titanium, niobium, etc. Composites reinforced with particles of the order of one or tens of microns are widely considered in the works, since microparticles provide more uniformly distributed phase in a Ni matrix than nanoparticles (Domitner et al. (2022), Wu et al. (2013)). Nanoparticles often have poor adhesion to the Ni matrix. They form aggregates, that lead to a decrease in the material strength and plasticity. However, the composites with a nanoscale reinforcing phase evenly distributed in the Ni matrix bulk are extremely promising, since the mechanical properties of such materials increase significantly. At the moment, a number of research groups are developing new approaches to the production of metal matrix composites with improved performance characteristics (Gopalakrishnan and Murugan (2012), Hashim (2012), Zemtsova et al. (2021)). High-temperature sintering and hot pressing have significant limitations when using them as a method for producing metal matrix composites, due to excessive grain growth (Lee at al. (2006)) Also, the combination of a matrix and a reinforcing component in one material inevitably encounters interfacial interaction. One of the new approaches being developed is selective laser melting. The article Gua et al.(2019) discusses Ni matrix composites reinforced with TiC with a particle size of ca. 90 nm, obtained by SLM. The use of the reinforcing phase nanoparticles increased the material strength by almost 2 times, while the nanohardness also increased by more than 15%. However, unfortunately, the plasticity of such a composite is significantly reduced. As a result of our research, an approach was proposed to obtain a metal matrix composite using the process of surface structuring (chemical assembly) and the method of powder metallurgy. The developed approach made it possible to obtain a composite where TiC nanostructures of 2-4 nm in size are evenly distributed in the Ni matrix bulk. The absence of interfacial boundaries between the particles of the Ni matrix and the carbide nanostructures made it possible to minimize the internal porosity. This allows not only to increase the strength properties of the composite, but also to preserve the material plasticity, which increases their suitability for processing. 1. Materials and methods 1.1. Synthesis of the reinforcing phase of TiC nanostructures on Ni particles TiC nanolayer on a Ni matrix was synthesized by the ALD method. ALD allows for the cyclic chemical assembly of TiC nanolayers (nanostructures) on a dispersed Ni matrix by irreversible chemisorption. Ni particles (50 microns) were placed in a gas-phase reactor and the surface was chemically treated in an inert atmosphere. At the first stage, the surface was standardized with aluminum chloride. It is the most effective reagent for removing the oxide layer and introducing active hydroxyl groups (-OH) for subsequent surface reactions. The synthesis was carried out at 350 °C for 30 minutes. • [Ni]a – OH + AlCl 3 + H 2 O = • [Ni]a – O - Al(OH) 2 + 2HCl