No abstract

The titanium and its alloys can be subjected to surface treatment, including laser treatment. In this work a new laser treatment at cryogenic conditions of Ti6Al4V alloy has been described. The work has been aimed at establishing whether such surface treatment could be suitable for implants working under wear in biological corrosive environment. The remelting has been made with the use of CO2 continuous work laser at laser power between 3 and 6 kW, at scan rate 0.5 and 1 m/s. The microstructure, surface topography, hardness, microhardness and wear linear rate and mass loss under tribological tests made in Ringer`s solution have been made. The results have shown that despite the surface cracking the tribological properties in simulated body fluid have been substantially improved.

The main objective of here presented research is a design the scaffold/porous titanium (Ti) alloy based composite material demonstrating better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants. The development of such material is proposed by making a number of consecutive tasks. Modelling the mechanical, biomechanical and biological behavior of porous titanium structure and an elaboration of results is performed by mathematical methods, including FEM and fuzzy logic. The development of selected Ti-13Zr-Nb alloy with designed porosity and no harmful effects is made by powder metallurgy (PM) with and without space holders, and by rapid prototyping with an use of selective laser melting (SLM). The development of an oxidation technology resulting in high corrosion resistance and bioactivity is carried out by electrochemical oxidation, gaseous oxidation and chemical oxidation, and their combination. The HA depositon is made by electrochemical and chemical (alternate immersion) methods. The core material is designed as a combination of natural polymer and bioceramics in order to allow slow dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing local inflammation processes, and sustaining the mechanical strength close to that of non-porous material.

The main objective of here presented research is to develop the titanium (Ti) alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants, e.g. hip joint and knee joint endoprosthesis. The development of such materials is performed through: modeling the material behaviour in biological environment in long time and developing of new procedures for such evaluation; obtaining of a Ti alloy with designed porosity; developing of an oxidation technology resulting in high corrosion resistance and bioactivity; developing of technologies for hydroxyapatite (HA) deposition aimed at composite bioactive coatings; developing of technologies of precipitation of the biodegradable core material placed within the pores. The examinations of degradation of Ti implants are carried out in order to recognize the sources of both early allergies and inflammation, and of long term degradation. The theoretical assessment of corrosion is made assuming three processes: electrochemical dissolution through imperfections of the anodic oxide layer, diffusion of metallic ions through the oxide layer, and dissolution of oxides themselves. In order to increase the biocompatibility, the toxic elements, aluminium (Al) and vanadium (V) are eliminated. The experiments have shown that titanium -zirconium -niobium (Ti-Zr-Nb) alloy may be a such a material which can also be prepared by both powder metallurgy (P/M) technique and selective laser melting. The porous (scaffold) Ti-Zr-Nb alloy is now obtained by powder metallurgy, classical and with space holders used before melting and decomposed, or remained during melting and removed by subsequent water dissolution. The oxidation of porous materials is performed either by electrochemical technique in special electrolytes or by chemical and/or hydrothermal method in order to obtain the optimal oxide layer well adjacent to an interface, preventing the base metal against corrosion and bioactive because of its nanotubular structure, permitting injection of some species into the pores. The Ca, O and N ion implantation or deposition of zirconia sublayers may be used to increase the biocompatibility, bioactivity and corrosion resistance. The HA coating obtained by either electrophoretic, biomimetic or by sol-gel deposition should result in gradient structure similar to bone structure, possessing high adhesion strength. The core material of the porous material should result in a biodegradable material, allowing slower dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing local inflammation processes, sustaining the mechanical strength close to that of non-porous material.

The purpose of this paper is to demonstrate the method of laser remelting at cryogenic conditions of the SUPERSTON alloy and its influence on microstructure and cavitation wearing. The cavitation test was performed using the rotating disc facility in IPM PAN Gdansk. During the cavitation test, the mass loss of the material with different parameters of laser remelting was determined. Surface and cross-section microstructure of the SUPERSTON alloy after laser treatment and cavitation test were observed by scanning electron microscope. The cavitation resistance of the remelted SUPERSTON alloy was approximately 40% higher in comparison to the base material.