Influência do tratamento térmico sub-βtrans na dureza e na microestrutura de implantes dentais de Ti-6Al-4V ELI produzidos por manufatura aditiva a laser
Influence of sub-βtrans heat treatment on the hardness and microstructure of Ti-6Al-4V ELI dental implants produced by laser additive manufacturing
José Alex Gonçalves de Galiza, Carlos Nelson Elias, André Rocha Pimenta
Resumo
O uso dos implantes dentais de titânio para a reabilitação total ou parcial da função mastigatória é uma prática clínica usual na odontologia. Estes implantes possuem osseointegração e são produzidas por usinagem de barras de titânio.
A possibilidade do emprego da manufatura aditiva (MA) para fabricar peças complexas abre a possibilidade da fabricação de implantes personalizados. Uma desvantagem da MA dos metais é que os produtos necessitam de tratamento térmico para alívio das tensões residuais oriundas do rápido resfriamento durante a manufatura. O objetivo do presente trabalho foi produzir implantes dentais de Ti-6Al-4V ELI por MA e analisar a influência do tratamento térmico sub-βtrans na dureza e na microestrutura. Os implantes foram submetidos aos tratamentos térmicos nas temperaturas de 400, 450 e 500 o C, as quais são inferiores à de transformação de fase α-β (sub-βtrans) da liga. Antes e após os tratamentos térmicos foram realizadas análises da microestrutura dos implantes por microscopia óptica e eletrônica de varredura, quantificadas as temperaturas de transformação de fases por calorimetria diferencial de varredura, identificadas as fases por difração de raios-X, medidos os tamanhos dos grãos e determinada a microdureza Vickers. Os dados de microdureza e tamanho dos grãos foram submetidos à análise estatística. Os resultados mostraram que todos os tratamentos térmicos alteraram a microestrutura e a microdureza dos implantes. As alterações mais relevantes na microestrutura foram das amostras tratadas a 500 o C, indicando que este tratamento térmico induz maior alívio de tensões sem redução da dureza dos implantes.
Palavras-chave
Abstract
The use of titanium dental implants for the total or partial rehabilitation of masticatory function is a common clinical practice in dentistry. These implants have osseointegration and are produced by machining titanium bars. The possibility of using additive manufacturing (MA) to make complex parts opens up the possibility of manufacturing custom implants. A disadvantage of the Ti alloy MA is that the products require heat treatment to relieve residual stresses arising from rapid cooling during manufacture. The present work aimed to produce dental implants of Ti-6Al-4V ELI by MA and to analyze the influence of sub-βtrans heat treatment on hardness and microstructure. The implants were subjected to heat treatments at temperatures of 400, 450, and 500 o C, which are inferior to the transformation of the α-β phase (sub-βtrans) of the alloy. Before and after the heat treatments, microstructure analyzes of the implants were performed by optical and scanning electron microscopy, the phase transformation temperatures were quantified by differential scanning calorimetry, the phases were identified by X-ray diffraction and the Vickers microhardness was determined. The microhardness and grain size data were subjected to statistical analysis. The results showed that all heat treatments changed the microstructure and microhardness of the implants. The most relevant changes in the microstructure were in the samples treated at 500 o C, indicating that this heat treatment induces greater stress relief without reducing the hardness of the implants.
Keywords
Referências
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Submetido em:
05/11/2020
Aceito em:
16/06/2021
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