Interdiffusion in V aluminides and determination of kinetic parameters

Author(s)

Vitória de Melo Silveira

• Document type: Master's Dissertation
• Press: Lorena.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de Lorena (EEL/ASDI)
• Defense date: 2024-03-01

Examining board members

Nabil Chaia; Nicolas David; Ana Sofia Clímaco Monteiro de Oliveira

• Advisor: Gilberto Carvalho Coelho; Nabil Chaia

Abstract

The study of kinetic phenomena is essential in order to understand physicalchemical and mechanical properties of materials, such as corrosion and oxidation resistances and creep. One of these phenomena is the diffusion, whose processes are widely explored in many industrial sectors, for example in surface heat treatments to improve properties that govern durability, safety and thermal stability. Applications of structural materials in environments with critical stress and temperature conditions, such as those found in aeronautical turbines and nuclear reactors, demand adequate mechanical properties and good chemical resistance. Vanadium-containing alloys, which is a metal with a high melting point and low density (compared to other refractory/reactive metals), are an example of materials that meet these requirements when used with certain protective layers, for example aluminum-based coatings. The present work aims to determine kinetic parameters, more specifically growth constants and interdiffusion coefficients, for vanadium aluminides. Al-V diffusion couples were constructed by the pack cementation technique, at temperatures of 800, 850, 900, 950 and 1000°C for times from 4 to 25 hours, during which the interdiffusion of the elements and the growth of the diffusion products occurred. The coated substrates were microstructurally characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energydispersive spectroscopy (EDS). Growth constants and interdiffusion coefficients were calculated at the mentioned five temperatures, by the Wagner model (1969), for the VAl3, V5Al8 and (V) phases. The values of the growth constants varied approximately between 10-13 and 10-10 cm2.s-1, while the interdiffusion coefficients ranged from 10-12 to 10-11 cm2.s-1. The kinetic data obtained here can be used to contribute to the construction of kinetic databases, crucial for assessing the lifespan of materials in high-temperature applications. (AU)

• FAPESP's process: 22/06285-6 - Interdiffusion in V aluminides and determination of kinetics parameters
• Grantee: Vitória de Melo Silveira
• Support Opportunities: Scholarships in Brazil - Master