Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Helium and deuterium irradiation effects in tungsten-based materials with titanium N. Catarino a, ⁎ , M. Dias a , J. Lopes b , I. Jepu c , E. Alves a a Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal b Instituto Superior de Engenharia de Lisboa (GIAAPP/ISEL), Portugal c National Institute for Laser, Plasma and Radiation Physics (NILPRP), Magurele 077125, Romania ARTICLE INFO Keywords: Tungsten Titanium Deuterium inventory Helium implantation ABSTRACT Pure Tungsten (W) will be used as plasma facing component in fusion devices due to its high melting point, good thermal conductivity and low sputtering yield. However, its structural application as plasma facing component (PFC) is still restricted by its low fracture toughness associated with the high ductile to brittle transition tem- perature (DBTT). In the present study tungsten‑titanium (W-Ti) samples were produced by Ti implantation at room temperature and 500 °C with a constant fluence of 2 × 10 21 at/m 2 and an energy of 100 keV. In order to understand the fundamental mechanisms which govern the behavior of defect dynamics in tungsten under reactor conditions, W-Ti materials were implanted at room temperature with 10 keV of He + with a constant fluence of 5 × 10 21 at/ m 2 and 5 keV of D + with fluences in the range of 0.1 × 10 21 –5 × 10 21 at/m 2 . Surface structure and morphology changes were investigated by scanning electron microscopy and X-ray diffraction. Rutherford backscattering spectrometry, nuclear reaction analysis and thermal desorption spectroscopy methods were used to provide information about the distribution of Ti, He and D on W. No changes in the microstructure were observed after Ti implantation in the W plates. NRA analysis showed that D retention in the W-Ti samples is higher after sequential He and D implantation when compared with single D implantation. The diffractogram of W-Ti samples implanted with He evidence a broadening of the W peaks. This effect is believed to be associated with the high volume fraction of the bubbles that may cause internal stress fields inducing extended defects like dislocations which distort the crystal lattice. 1. Introduction Tungsten is considered one of the best materials for plasma facing applications in nuclear fusion devices, due to low activation, high melting point, low sputter erosion and low tritium retention/co-de- position [1]. It has excellent corrosion resistance and at temperatures over than 1650 °C has the highest tensile strength. However the ducti- lity becomes the major issue [2], limiting the use of W to operate at temperatures below the ductile to brittle transition temperature (DBTT) value which increases with neutron irradiation [3]. A strategy to in- crease the fracture toughness of W is to alloying this element with other refractory metals, maintaining the low neutron activation cross section. One good example is W-Re alloy, in which the presence of rhenium reduces radiation swelling, and increases ductility and hardness of W [4]. After rejecting the W–Re alloys for economic and practical reasons, other refractory metals like Ti (W-Ti) and V (W-V) were considered with suitable characteristics for divertor applications. The mechanical behavior of W–Ti alloy in the range 25–1000 °C has been reported by Aguirre et al. [5], showing enhanced strength, toughness, and hardness at ambient temperature. Some metastable titanium phase such as α′, α″ or ω that could influence the mechanical behaviour of W-Ti alloys has been reported by Savoini et al. [6]. The review conducted by Rath et al. [7] highlighted that some titanium alloys undergo a tensile ductility loss when tested near the β-α transformation. In the present work W-Ti samples were produced by Ti implantation at room temperature (RT) and 500 °C with a fluence of 2 × 10 21 at/m 2 and an energy of 100 keV. In order to understand the fundamental mechanisms governing the behavior of defect dynamics under reactor conditions, the produced W-Ti set was implanted at room temperature with 10 keV of helium (He) with a fluence of 5 × 10 21 at/m 2 and 5 keV of deuterium (D, refers to isotope of hydrogen, 2 H) with fluences in the range 10 20 –10 21 at/m 2 . Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy was used to investigate the sur- face morphology and X-ray diffraction was used to study the structural https://doi.org/10.1016/j.surfcoat.2018.03.015 Received 27 October 2017; Received in revised form 7 March 2018; Accepted 8 March 2018 ⁎ Corresponding author. E-mail address: norberto.catarino@ctn.tecnico.ulisboa.pt (N. Catarino). Surface & Coatings Technology xxx (xxxx) xxx–xxx 0257-8972/ © 2018 Published by Elsevier B.V. Please cite this article as: Catarino, N., Surface & Coatings Technology (2018), https://doi.org/10.1016/j.surfcoat.2018.03.015