Papers by Keyword: Titanizing

Abstract: Austenitic stainless steel 316L is widely used in implantology due to its biocompatibility, a lower price than titanium and because can be easily mechanically machined. The drawback is due to the fact that toxic nickel and chromium ions are released into human body fluids. Our proposal is to coat 316L austenitic stainless steel with biovitroceramic layers made of oxide system SiO₂, B₂O₃, Na₂O, CaO, TiO₂, P₂O₅, K₂O, Li₂O and MgO by means of an enamelling procedure in order to hinder the release of Ni and Cr ions from the metallic implant surface toward the tissue around the implant. In order to achieve a firm adherence of biovitroceramic layer onto the metal, with an optimal composition for biocompatibility and bioactivity, we have modified the steel surface by a titanizing thermochemical treatment. The adherence of the biovitroceramic layer to the 316L stainless steel with modified surface is very good. The biovitroceramic coating - metallic substrate couple was studied by optical microscopy, electron microscopy (SEM and EDAX), X-ray diffraction analysis and microhardness trials.

Abstract: Q195 steel was treated with titanizing followed plasma nitriding by glow plasma alloying technology using single pulse power supply. The corrosion resistances of titanizing sample and titanizing + ion nitrided sample were studied. The results show that the alloying layer is 200 μm in depth and organization is α-Fe solid solution containing Ti by plasma titanizing technology using single pulse power supply. An obvious reactive diffusion dividing line formed between alloying layer and the substrate. It shows that diffusion phenomenon happened in process of titanizing. The morphology of Ti alloy layer was columnar crystals. The content of Ti on the surface is up to 5 wt%. And the Ti content of alloying layer is in a decreasing from the surface to the inner on a gradient distribution. The phase structure of titanizing layer is composed of Fe₂Ti, Fe-Ti and TiC phases. The phase structure of titanizing + ion nitrided sample was obviously TiN phase and a few Fe-Ti phase. The surface hardness of untreated carbon steel is 110 HV and that of the alloying layer of titanizing is 310HV. The surface hardness of titanizing + ion nitrided sample is 1800HV. The corrosion resistance of titanizing sample is increased 12.15 times compared with the untreated sample and 1.42 times compared with 18-8 stainless steel in H₂SO₄ solution; The corrosion resistance of titanizing + ion nitrided sample is increased 7.444 times compared with the untreated sample and as well as 18-8 stainless steel in H₂SO₄ solution.

Abstract: In the present work, Ti and Ti-6Al-4V were PIRAC nitrided at the relatively low temperatures of 700-850°C. To obtain thicker TiN layers, 3 stage PIRAC based coating was applied: (1) PIRAC nitriding followed by (2) PIRAC titanizing followed by (3) additional PIRAC nitriding. The microstructure and phase composition of the obtained surface layers were characterized employing X-ray diffraction and scanning electron microscopy with chemical analysis (SEM/EDS). Bending test was employed to evaluate the coatings adhesion to the substrate. Lower PIRAC nitriding temperatures yielded smoother TiN coatings with a more gradual microhardness decrease from the surface to the bulk. All PIRAC TiN based coatings have excellent adhesion to substrate – no delamination of the coating in bending tests was observed. The best combination of microhardness and adhesion was obtained using 3 stage PIRAC process.

Abstract: In this work, some surface properties of AISI M2 steel were improved by a thermoreactive deposition process. Gas nitriding was realized on AISI M2 steel at 550°C for 2 h in an ammoniac atmosphere and then, titanizing treatment performed on pre-nitrided steel in the powder mixture consisting of ferro-titanium, ammonium chloride and alumina at 1000°C for 1-4 h. Structural characterization of titanium nitride layer formed on the surface of AISI M2 steel was carried out by using optical microscopy, scanning electron microscopy, electron microprobe and Xray diffraction (XRD) analysis. The hardness measurements of titanium nitride layer were conducted under 10 g loads by using Vickers microhardness indenter. Structural analysis studies showed that titanium nitride layers formed on the AISI M2 steel samples were smooth, compact and homogeneous. XRD analysis show that the coating layer formed on the steel samples includes TiN, Fe6Mo7N2, C0.7N0.3Ti, C0.3N0.7Ti and V2N phases. The hardness of titanium nitride layers formed on the steel samples is between 2040±186 and 2418±291 HV0.01. The thickness of titanium nitride layer formed on the steel samples ranged from 3.86±0.43 9m to 6.13±0.47 9m, depending on treatment time.