Oxygen diffusion saturation of hafnium with the different surface layer

Hafnium is used for the production of control rods and protective screens in nuclear reactors after its hot plastic deformation and final thermochemical treatment. This research presents the experimental results of the influence of the surface layer state on the oxygen diffusion saturation of hafnium during thermochemical treatment in an oxygen-containing gas medium. Two cases of the surface layer state were considered: in the initial (delivery) state and after grinding, where 50 μm of the surface layer was removed. Differences between the hardness distributions in the near-surface layer of HFE-1 hafnium after thermochemical treatment in an oxygen-containing gas medium were shown. It was found that thermochemical treatment of hafnium with a surface layer in its initial state leads to an increase of hardness in the near-surface layer compared to the surface: i.e., the near-surface layer hardness increases to a depth of 5 - 7 μm, and then gradually decreases to the matrix (core) hardness. It was determined that the fatigue life of hafnium after thermochemical treatment depends on the surface layer state. A 6.5 times higher fatigue life after thermochemical treatment of hafnium samples was fixed with a grinded surface compared to hafnium samples without grinding

Corrosion behavior of titanium oxynitrided by diffusion and magnetron sputtering methods in physiological solution

This work presents the study of the corrosion-electrochemical behavior of titanium alloy Grade 2 treated with combined coatings—presaturation with nitrogen diffusion layer by thermal-chemical treatment, oxygen diffusion layer by thermal-chemical treatment, and a titanium oxynitride (TiN x O y) coating deposited by magnetron sputtering—in physiological solution. Structural analysis has shown that TiN x O y can be represented as a face-centered cubic (fcc) structure in which nitrogen atoms are replaced by oxygen atoms, or oxygen atoms are replaced by nitrogen atoms. Presaturation of titanium Grade 2 with oxygen and nitrogen leads to the formation of TiN x O y with near equiatomic composition at subsequent oxynitriding by magnetron sputtering. Rutherford backscattering spectrometry (RBS) measurements show the homogeneity of the coating composition. The surface of titanium Grade 2 with a nitrogen diffusion layer presents the highest lightness factor and reflectivity in the range of the visible spectrum. Diffusion presaturation of titanium Grade 2 with either oxygen or nitrogen provides better adhesion of TiN x O y film to substrate. The presence of an oxygen diffusion layer leads to a stronger bond. It was found that a TiN x O y coating increases the corrosion resistance (isotonic solution of 0.9 % sodium chloride (NaCl)) 1.2 times as compared to a nontreated alloy. When the titanium alloy was presaturated with oxygen or nitrogen, the combination of the Physical Vapor Deposition (PVD) oxynitride coating and the diffusion layer, 50?m thick, assists in additional enhancement of corrosion properties 1.5 to 3 times.info:eu-repo/semantics/publishedVersio