Titanium alloys elaboration with superelastic properties for cladding tests implants – ELASTICITE

The innovations expected reside in:
-the transformation of selected alloy powder, first technological lock;
- the complete characterization of the alloy after transformation into
powder, then remelting under laser beam (process CLAD) to verify its
adequacy to the applications;
-the proposal for a new joint implants designs tailor-made for the
patient's anatomy and the technical requirements of processing methods.
It is the atomization under inert gas (Ar) used for the obtaining of the
powder.
The characterizations after transformations will be:
-metallurgical (XRD, metallography, SEM);
-mechanical (tensile, flexural yield strength and ultimate strength,
mechanical fatigue, nano-indentation for the measurement of the moduli of elasticity in the interface region to the os, scratch an
exploratory);
-biological (cell cultures) to check the biocompatibility after
transformations.

As of October 01, 2013, the manufacture of the alloy with the expected characteristics used to initiate its transformation in powder additive manufacturing CLAD process-compatible was performed.
At the same time, the digital 3D modeling of charge transfer from
the implant to bone must be refined to propose in June 2014, the
manufacture of a demonstrator using the properties expected of
the alloy in a geometry optimized anatomically.

Where processing into powder would be a blocking point, other avenues of research are the study so as to ensure the possibility of a demonstrator
at the end of project. The development of alloy under the laser beam
from a dosage accurate mixing of powders, as mentioned in the initial
scientific dossier, is a possible opening.
With the help of surgeons associated with the consortium, the
demonstrator will take the form of a femoral stem of a total hip replacement.

The date of October 01, 2013, the consortium has not enough studying time to propose scientific publications.

In this project, the consortium wishes to develop joint prostheses of new generation made of a new titanium alloy, shaped by a laser additive building (CLAD® process, see description in appendix). The innovative combination of the TiNb titanium alloy specific properties and CLAD® process will substantially reduce the source of prostheses loosening.
The metastable titanium alloys developed by LEM3 partner exhibit a Young modulus much closer to that of bone, compared to the Ti alloys currently in use. These new biomimetic alloys are made from elements considered as bio-inerts (Nb, Zr, Y, N, Si). Different optimized microstructures based on thermo-mechanical treatments have resulted in a very low Young’s modulus (20 – 40 GPa) and high resistance.
The CLAD® process allows shaping parts that conventional process (e.g., forging, casting) cannot; its flexibility enables the manufacturing of biomimetics shapes applicable to individual parts close to the morphological parameters of patients.
The major technological advance relies in the metallurgical behavior of the alloy TiNb considered. Indeed, it is mandatory to validate the remained material properties in the different processing steps (pre-alloy ingot, atomizing, CLAD development of structure, etc.). Volumes and surfaces will therefore be exhaustively characterized (metallurgical, mechanical, electrochemical and biological) as there is currently no data available in the literature.
The second important aspect developed in this project concerns the multi-materials concept. The alternative implementation is to start with a smaller piece of a standard Ti alloy manufactured by conventional routes, particularly in the metaphysal portion of a joint implant. Therefore, only additive forms manufactured with CLAD® will fill the volume in the medullary canal, adapting the prosthesis to the patient’s morphology, limiting hence the TiNb volume only to the parts in contact with bone.
In order to achieve this goal, the additive building with TiNb alloy start on a Ti conventional alloy part. The understanding, control and optimization of how the intermediate layers are built with respect to specific metallurgical behaviors will be studied and fully characterized.
This program aims at proposing a new concept for developing customized prostheses, leading to a major change in the current industrial scheme. The concept will promote an increase in the lifetime of the implant and a better quality of life of patients, because of an enhanced osteointegration: gradient in properties, biomimetic properties, localized functional surfaces.