ION NITRIDING OF TITANIUM-ALPHA PLUS BETA-ALLOY FOR FUSION-REACTOR APPLICATIONS

The titanium alpha plus beta alloy, Ti-6Al-4V, has been plasma nitride d at 1033 K in pure nitrogen to produce a 9 mu m thick surface nitride zone, followed by a 5 mu m thick Al-enriched zone and a 100 mu m thic k nitrogen diffusion zone. X-ray diffraction and Auger electron spectr oscopy indicate that the nitride zone consists of two layers: a thin T iN layer at the surface followed by a Ti2N layer, In preliminary tests , the deuterium retention of nitrided titanium specimens was determine d after exposure to fluences of 4 x 10(25) m(-2), 60 eV D+ ions at 440 K and of 2 x 10(25) m(-2), 800 eV D+ ions at 623 K, The results are c ompared to the retention found for similar exposure of the untreated a lloy and to model simulations. Implications for the use of these mater ials in a fusion environment are discussed. (C) 1998 Elsevier Science B.V.