EFEITO DA TEMPERATURA DE AQUECIMENTO NA DIFUSÃO DE FE-AL-SI EM REVESTIMENTO AL-SI DURANTE A ETAPA DE AUSTENITIZAÇÃO EM UM PROCESSO DE ESTAMPAGEM A QUENTE
EFFECT OF HEATING TEMPERATURE ON FE-AL-SI DIFUSION IN AL-SI COATING DURING THE AUSTENITIZATION STAGE IN A HOT PRINTING PROCESS
Fabrício Moreira Cerqueira, Carlos Augusto de Oliveira, Bruno Neto, Laura Ribeiro Martins
Resumo
A implementação continua de normas de segurança e emissão de CO2 em veículos automotivos têm impulsionado a busca pela redução de peso e aumento de segurança. Por isso, o desenvolvimento de aços de elevada resistência mecânica se destaca como os mais aplicáveis. Essas peças apresentam complexidade geométrica e necessitam de maior resistência mecânica, geralmente, produzidas por estampagem a quente. Os aços empregados, nesse caso, possuem adição de boro, como o 22 MnB5. Pesquisas relacionadas ao desenvolvimento de revestimentos metálicos têm sido realizadas, a fim de resistirem os esforços mecânicos e tratamento térmico. Assim, o revestimento Al-Si composto por multifases de Al-Si-Fe são largamente empregados em aços, pois durante a austenitização ocorre à formação de novas fases pela inter-difusão de Fe e reações de solidificação definindo a microestrutura final. Amostras do aço 22MnB5 revestidas (Al-Si) foram tratadas entre temperaturas de 500 a 900°C. Através de análises de microscopia (MEV) e GDOES foi possível identificar a difusão de Fe ao longo da camada de revestimento, e baseando-se no diagrama de fases ternárias e em simulações, foi proposto um caminho de entendimento da transformação do revestimento Al-Si pela difusão do ferro
Palavras-chave
Abstract
Currently, continuous implementation of safety and CO2 emission standards in automotive vehicles has driven the search for weight reduction and safety enhancement solutions. In this context, the development of high mechanical strength in steels has been highlight as the most applicable. Those pieces have complex geometric and require greater mechanical strength, thus they are produced by hot stamping. The selected steels for this application have addition of boron, such as 22 MnB5. In parallel, researches related to the development of metallic coatings capable of withstanding mechanical stresses and heat treatment have been carried out. The Al-Si coating composed of Al-Si-Fe multiphases has been strongly used, because during the austenitization occurs to the formation of new phases by the inter-diffusion of Fe and solidification reactions defining the final microstructure. Samples of coated 22MnB5 steel (Al-Si) were treated between temperatures of 500°C to 900 °C. Through the analysis of microscopy (SEM) and GDOES it was possible to identify the diffusion of Fe along the coating layer. Based on the ternary phase diagram and the simulations, it was possible to propose a way of understanding the transformation of the Al-Si coating by the diffusion of the iron.
Keywords
References
1 Turetta A. Investigation of thermal, mechanical and microstructural properties of quenchenable high strength steels in hot stamping operations [thesis]. Padova: Univesita’ Degli Studi di Padova; 2008.
2 ArcelorMittal. [Catálogo de produtos]. São Paulo: ArcelorMittal; 2017.
3 Raynor GV, Rivilin VG. Phase diagrams of ternary iron alloys: phase equilibria in iron ternary alloys. Materials Park: ASM International; 1988. p. 122-139.
4 Pontevichi S, Bosslet F, Barbeau F, Peronnet M, Viala JC. Solid-liquid phase equilibria in the Al-Fe-Si system at 727°C. Journal of Phase Equilibria and Diffusion. 2004;25(6):528-537.
5 Stefaniay V, Griger A, Turmezey T. Intermetallic phases in the aluminium-side corner of AlFeSi-Alloy system. Journal of Materials Science. 1987;22:539-546.
6 Turmezey T, Stefaniay V, Griger A. AlFeSi phases in Al. Key Engineering Materials. 1990;44-45:57-58.
7 Vierstraete R, Ehling W. Development of laser decoating process for fully functional Al-Si coated press hardened steel laser welded blank solutions. In: Proceedings of the Fifth International WLT-Conference on Lasers in Manufacturing; 2009; Munich. Munich: TIB (Leibniz information centre for Science and technology – University library); 2009.
8 Grigorieva R; Drillet P. Study of phase transformation in the Al-Si coating during the austenitization step [relatório interno]. São Paulo: ArcelorMittal; 2011.
9 Koster U, Liu W. Non-cryst. Solids. 1993;153-154:446-452.
10 Kobayashi S, Yakou T. Control of intermetallic compound layers at interface between steel and aluminum by diffusion-treatment. Materials Science and Engineering. 2002;A338:44-53.
11 Gupta SP. Intermetallic compound formation in Fe-Al-Si ternary system: part1. Materials Characterization. 2003;49:269-291.
12 Maitra T, Gupta SP. Intermetallic compound formation in Fe-Al-Si ternary system: part 2. Materials Characterization. 2003;49:293-311.
13 Guesdon. Synthèse sur la métallurgie et les mécanismes de formation des revêtements aluminiés [relatório interno]. Maiziéres-les -Metz: Sollac: 1997. GEN93-CED5.
14 Eggler G, Auer W, Kaesche H. Journal of Materials Science. 1986;21:3348-3350.
15 Windmann M, Rottger A, Theisen W. Phase transformation at the interface between a boron alloyed steel substrate and Al-rich coating. Surface and Coatings Technology. 2013;226:130-139.
16 Windmann M, Rottger A, Theisen W. Formation of intermetallic phases in Al-coated hot-stampped 22MnB5 sheets in terms of coating thickness and Si content. Surface and Coatings Technology. 2014;246:17-25.
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