Spontaneous formation of multilayer refractory carbide coatings in a molten salt media

Refractory materials hold great promise to develop functional multilayer coating for extreme environments and temperature applications but require high temperature and complex synthesis to overcome their strong atomic bonding and form a multilayer structure. Here, a spontaneous reaction producing sophisticated multilayer refractory carbide coatings on carbon fiber (CF) is reported. This approach utilizes a relatively low-temperature (950 °C) molten-salt process for forming refractory carbides. The reaction of titanium (Ti), chromium (Cr), and CF yields a complex, high-quality multilayer carbide coating composed of 1) Cr carbide (Cr3C2), 2) Ti carbide, and 3) Cr3C2 layers. The layered sequence arises from a difference in metal dissolutions, reactions, and diffusion rates in the salt media. The multilayer-coated CFs act as a permeable oxidation barrier with no crystalline degradation of the CFs after extreme temperature (1,200 °C) and environment (oxyacetylene flame) exposure. The synthesis of high-quality multilayer refractory coating in a fast, efficient, easy, and clean manner may answer the need for industrial applications that develop cheap and reliable extreme environment protection barriers.

RESEARCH OF THE MECHANISM OF COMPACTION OF MIXTURES OF POWDERS OF REFRACTORY CARBIDES WITH A METALLIC BOND IN EXPLOSIVE PRESSING ON A METAL SUBSTRATE

The results of investigations of the features of the behavior of the components of mixtures of refractory carbide powders with metals during explosive pressing are presented. It is shown that the main factor determining the compaction of mixtures is the dynamic flow of one of the phase components of the mixture into the initial pores of the powder. As the phase component of the mixture, the movement of which limits the degree of compaction and leads to the formation of a continuous matrix in the structure of the material pressed by the explosion, both the metal binder and the carbide component of the material can act.

Synthesis and Spark Plasma Sintering of Nanosized Refractory Carbide/Nitride Powders

In the present study, seven refractory compounds - TiC, NbC, TaC, WC, Ti (C,N), (Ti,Nb)(C,N) and TiN - have been produced by plasma-chemical synthesis and carbothermal reduction process of a precursor prepared by sol-gel method. The phase composition, crystallite size, morphology and specific surface area of the synthesized powders are investigated by XRD, TEM, SEM and BET respectively. Spark plasma sintering (SPS) method (up to 1850 °C, heating rate of 100 °C/min and dwelling time of 5 min.) are used for investigation of compacting of these compounds. Characteristics of the obtained ceramic materials are provided.

The formation mechanism of refractory carbide phases in the complex-alloy heat-resistant steels during carburization.

The laws of carbide phases nucleation were analyzed in the context of the complex-alloy heat-resistant steels carburization. Numerical experiments and metallographic investigations of steel and model alloys diffusion layers structures were applied to determine the predominant mechanism for the formation of refractory carbide phases.