**4.2 CoCr alloy**

158 Biomedicine

*Recovery System (PRS)*. The rest of powder is wiped away by a jet of compressed air charged with particles of the same material that the implants are made of (so as to prevent implant contamination). After cleaning the implant, the support structure is removed by hand (it is designed to have small contact surface with implant and be easy to eliminate). Also, if necessary, additional machining and/or polishing of certain surface or zone is performed. As can be seen from this analysis of the supply chain, main advantages of additive

avoid human errors since the batch of models is stored in electronic way and

 make hundreds of implants in a week time with very optimized price, depending on size, since the same batch can be built again without additional preparation.

The raw material in EBM is powder. Hence, it is reasonable to expect that the processed material contains residual porosity. However, the processed material on EBM is almost 100% dense because of complete local fusion of powder. Experimental results are offered to illustrate the capabilities of EBM in biomedical applications through two widely used materials: Ti6Al4V and CoCr ASTM F75 which are commercially available for processing on EBM. More materials are under development which will be mentioned in the 'Future

Ti6Al4V is a widely used biomaterial for many medical applications (Biomet, 2009), (Oshida, 2007), (Bronzino, 2006). Experimental results show that the properties of full-dense Ti64 processed on EBM fulfill the corresponding norm for medical implants (ISO, 2010), (ASTM,

Table 1. Comparative view of Ti64 properties: Electron Beam Melting (EBM) vs wrought Ti64.

However, the important advantage of Additive Manufacturing is the capability of producing designed porous material that can be combined with solid material in a single implant. Hence, it is interesting to take a look at the properties of porous material made on EBM. According to a several studies (Petrovic, 2011), (Parthasarthy, 2010), the properties of

**Standars, 2010) Ti64 (EBM) Ti64 (cast) (ASTM, 2010)** 

 *value-added design* (porous surface with controlled porosity), *use of additive rather than subtractive fabrication* which allows:

recycling of major part of material (up to 98%);

2010) and are even superior to casted titanium alloys (Table 1).

**Yield strenght [Mpa]** 760 849 825 **Elongation [%]** 10 15 10 **Area reduction [%]** - 37 15-25 **Young modulus [GPa]** - 125 -

**Properties Norm (ISO** 

much bigger geometrical freedom;

*automation* of the process, which permits to:

prepared for "load & play";

technologies are:

**4. Processed material** 

Developments' section.

**4.1 TiAl6V4 alloy** 

Cobalt Chromium is commonly used in fabrication of implants that are submitted to intensive wearing (knees, shoulders, elbows, etc.). Hence, it is very important for the material processed on AM to show good wearing resistance. For EBM CoCr that corresponds to ASTM F75 is commercially available. Experiments and tests have been made with this material (Petrovic, 2010) and confirm that the main mechanical properties comply with the corresponding norm (Table 3).


Table 3. Comparative view of CoCr F75 properties: Electron Beam Melting (EBM) vs corresponding norm.
