Improvement in fatigue strength of notched Ti-6Al-4V alloy by short-time heat treatment

Morita, Tatsuro; Tanaka, Satoshi; Ninomiya, Susumu

doi:10.1016/j.msea.2016.05.071

Cited by 19 publications

(14 citation statements)

References 11 publications

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“…Over the whole fracture surface, microcracks and striations perpendicular to the propagation direction can be seen in detail in figures 6(b) and (c) respectively. Multiple cracks were also reported in other studies [1,18,23]. A large number of striations on the fracture surface indicate plastic deformation.…”

Section: Resultssupporting

confidence: 77%

“…As per the study of Morita et al [18], the formation of these layers after plasma nitriding increases the surface hardness of the alloy, which in turn increases the resistance to movement of dislocations and as a consequence, increases the fatigue strength of the alloy. Rocha [19], reported that delay in crack nucleation in plasma nitrided specimens is due to the difference in Young modulus between the titanium alloy matrix (100 GPa) and the titanium nitrides formed on the plasma nitride surface (400 GPa).…”

Section: Resultsmentioning

confidence: 65%

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Effect of Plasma Nitriding on Fatigue Behavior of Ti-6Al-4V Alloy

Castro¹,

Couto²,

Almeida³

et al. 2018

Preprint

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The Ti-6Al-4V alloy is widely used in the manufacture of components that should have low density, high corrosion resistance, and fatigue strength. The fatigue strength can be improved by surface modification. The aim of this study was to determine the influence of plasma nitriding on the fatigue behavior of Ti-6Al-4V alloy with a lamellar microstructure (Widmanstätten type). Nitriding was executed at 720 °C for 4 hours in an atmosphere with N2, Ar and H2. Samples microstructure characterization was carried out by X-ray diffraction analysis, optical microscopy and scanning electron microscopy. The average roughness of the specimens was determined, and fatigue tests were executed in a bending-rotating machine with reverse tension cycles (R= -1). X-ray diffraction analysis revealed the matrix phases α and β, and the phases Ɛ-Ti2N and δ-TiN in the nitrided alloy. A nitrogen diffusion layer was formed between the substrate and the titanium nitrides. Plasma nitriding resulted in an increase in low cycle fatigue strength, whereas at high cycles, both conditions exhibit similar behavior. The fracture surface of the fatigue tested specimens clearly revealed the lamellar microstructure. The fracture mechanism appears to be due to cracking at the interface of α and β phases of the lamellar microstructure.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 65%

Effect of Plasma Nitriding on Fatigue Behavior of Ti-6Al-4V Alloy

Castro¹,

Couto²,

Almeida³

et al. 2018

Preprint

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“…As mentioned in the previous section, the columnar microstructure of the SLM materials was mainly composed of the α phase. This meant that rapid heating and cooling in the SLM process had a heat treatment effect similar to the short-time heat treatment 12,13,25) . Indeed, the static strength (yield strength and tensile strength) and the hardness of the SLM materials were much higher than those of W material ( Table 2).…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…This issue must be overcome in order to apply AM to various products including medical implants. Our previous studies showed that the fatigue strength of Ti-6Al-4V alloy (wrought material) was markedly improved by short-time heat treatment 12,13) , hybrid surface treatment 14,15) and their combination 16,17) . These treatments have a high potential to improve the fatigue strength of Ti-6Al-4V alloy produced by the AM method.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Properties of Ti-6Al-4V Alloy Produced by Selective Laser Melting Method

et al. 2017

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This study was conducted to comprehensively investigate the fundamental properties of Ti-6Al-4V alloy produced by the selective laser melting (SLM) method. The examined materials were three SLM materials having different axial directions. For comparison, wrought material of Ti-6Al-4V alloy was also examined. The results showed that the densities of the SLM materials were adequately high and more than 99.9% of that of the wrought material. The SLM materials possessed a columnar microstructure extending along the building direction. This microstructure was mainly composed of the acicular α martensite phase. Due to the generation of the ne α phase, the static strength of the SLM materials was markedly higher than that of the wrought material although their elongation was lower. There was anisotropy in the static strength and the ductility of the SLM materials. In spite of the higher tensile strength, the fatigue strength of the SLM materials was much lower than that of the wrought material since molding defects may induce stress concentration and accelerate the generation of fatigue cracks.

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“…corpos de prova não nitretados. Porém, para os valores de limite de fadiga, os corpos de prova nitretados apresentaram valores inferiores aos corpos de prova não nitretados, sendo esse comportamento também observado porZUO et al (2008).Uma possível explicação para uma maior vida em fadiga dos corpos de prova nitretados por plasma nos ensaios em tensões mais elevadas (fadiga de baixo ciclo) pode ter ocorrido devido à tensão residual compressiva formada pelas camadas de nitretos e da zona de difusão, inibindo assim a nucleação da trinca na superfície da liga, em conformidade com outro trabalho similar(RODRIGUEZ et al,2001).Conforme discutido porMORITA et al(2016), a formação dessas camadas após a nitretação por plasma aumenta a dureza superficial daliga, o CASSAR et al, 2016 , NOVOVIC et al,2004. N na região de fadiga de alto ciclo é mais evidente, e possível de ser identificada.…”

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Efeito da nitretação por plasma no comportamento em fadiga da liga Ti-6Al-4V

Castro¹

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Plasmas e Processos, onde foram feitas as nitretações a plasma, em especial ao Prof. Dr. Argemiro S. da Silva Sobrinho, Prof. Dr. Marcos Massi e Prof. Dr. Douglas Marcel Gonçalves Leite. À Dra. Gislene Martins do ITA pelos dias de companhia no reator, pelas caronas e conversas. À Escola de Engenharia Mackenzie, onde foram feitos os tratamentos térmicos. À pós-doutoranda Gisele Fabiane Costa Almeida pelo apoio e incentivo durante o mestrado, pelos conhecimentos divididos, acompanhamentos de diversas etapas deste trabalho e pela amizade. À doutoranda Camila Pucci Couto, pela amizade de longa data, grande incentivadora desse trabalho. Ao Mestre Mariano Castagnet pela ajuda no laboratório de ensaios mecânicos, revisão de diversos textos e apresentações e pela amizade. Ao Dr. Rene Ramos de Oliveira e Mestre Gleicy de Lima Xavier pela sempre disponibilidade, amizade e conversas. Ao Engenheiro Fabricio Mendes, pela usinagem dos corpos de prova de fadiga, e pela disponibilidade em ajudar sempre. Aos meus pais e marido, pois sem a ajuda e apoio deles, nada disso seria possível. "Nascer sabendo é uma limitação porque obriga a apenas repetir e, nunca, a criar, inovar, refazer, modificar. Quanto mais se nasce pronto, mais refém do que já se sabe e, portanto, do passado, aprender sempre é o que mais impede de que nos tornemos prisioneiros de situações que, por serem inéditas, não saberíamos enfrentar." Mario Sergio Cortella Palavras-chave: Liga de titânio Ti-6Al-4V, nitretação por plasma, fadiga ABSTRACT CASTRO, M.C.B. de. Nitriding plasma effect on Ti-6Al-4V fatigue behavior. 2018.X p. Tese (Mestrado em Tecnologia Nuclear) Instituto de Pesquisas Energéticas e Nucleares, São Paulo.The Ti-6Al-4V alloy presents excellent mechanical properties, low density, high toughness and corrosion resistance. However, surface treatments like plasma nitriding are widely used to improve the fatigue resistance of this alloy. Therefore, the aim of this work was to treat thermochemically Ti-6Al-4V alloy by means of plasma nitriding to verify its influence in fatigue properties and compare the results with the untreated ones. This surface treatment was performed with the purpose of retards the crack initiation. The plasma nitriding was performed in temperatures around 720°C for 4 hours, with a gas atmosphere N2, Ar and H2 (5:5:1). A heat treatment was made in the samples to obtain a Widmanstätten microstructure.The temperature used was 1050°C for 30 minutes. Microstructural characterizations of nitrided and non-nitrided samples were carried out using X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM). The XRD results of the nitrided sample showed the presence of the α, β, Ɛ-Ti2N, and δ-TiN phases. These analyses revealed a surface layer rich in nitrides on the surface, followed by a diffusion layer of nitrogen in the matrix. The surface roughness was compared between the nitrided and non-nitrided layer, and it was observed that the roughness increased 61% after the plasma nitriding. Fatigue tests were performe...

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Improvement in fatigue strength of notched Ti-6Al-4V alloy by short-time heat treatment

Cited by 19 publications

References 11 publications

Effect of Plasma Nitriding on Fatigue Behavior of Ti-6Al-4V Alloy

Effect of Plasma Nitriding on Fatigue Behavior of Ti-6Al-4V Alloy

Fundamental Properties of Ti-6Al-4V Alloy Produced by Selective Laser Melting Method

Efeito da nitretação por plasma no comportamento em fadiga da liga Ti-6Al-4V

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