ARCAM
  
– Arcam ASTM F75 CoCr
Arcam ASTM F75 CoCr 

General characteristics

Cobalt-based alloys have been used in demanding applications

for as long as investment casting has been available as an

industrial process. Arcams Electron Beam Melting technology

competes directly with investment casting and is a viable

choice for manufacturing complex parts in cobalt-based alloys.

The majority of investment castings made from the cobalt

super alloys are cast in an open atmosphere. With Arcams

Electron Beam Melting process the vacuum atmosphere provides

a controlled environment and enables superior material

properties in the manufactured parts.

CoCrMo alloys are widely used for medical prosthetic implant

devices. The alloys are especially used where high stiffness or a

highly polished and extremely wear-resistant material is

required. CoCrMo alloys are the materials of choice for applications

such as knee implants, metal-to-metal hip joints and

dental prosthetics.

Cobalt alloys also play an important role in the performance of

aero- and land-based gas turbines. While vacuum cast nickel

alloys predominate in the hot sections of modern aero turbine

engines, cobalt alloys are routinely specified

for particularly demanding applications

such as fuel nozzles and vanes for industrial

gas turbines.

Arcam ASTM F75 is a non-magnetic

CoCrMo alloy exhibiting high

strength, corrosion resistance, and

excellent wear resistance. It is widely

used for orthopaedic and dental

implants. Highly polished components

include femoral stems for

replacement hips and knee condyles.

Other cobalt medical implants

include acetabular cups and tibial

trays. In all cases, but especially in

hip components, material quality is

imperative as parts are heavily loaded

and subject to fatigue.

Arcam EBM system

Special characteristics

The Arcam ASTM F75 CoCr alloy is also suitable for Rapid

Manufacturing of production tools for injection moulding of

plastic parts. The high hardness of the material and the excellent

material qualities allow polishing components to optical

or mirror-like finishes, and ensures long tool life.

Tools can be built with complex geometries, and the conformal

cooling channels further enhance the tools life and increase

productivity, part and surface quality.

Applications

CoCr is typically used for:

Gas turbines

Orthopaedic implants

Dental implants

Powder specification

The Arcam ASTM F75 CoCr alloy powder for EBM is produced

by gas atomization and the chemical composition complies

with the ASTM F75 standards specification. The particle size is

45100 microns. This limitation of the minimum particle size

ensures safe handling of the powder.

Please refer to the Arcam MSDS (Material Safety Data Sheet)

for more information about the handling and safety of the

Arcam ASTM F75 CoCr alloy.

POST PROCESSING

Heat treatment

The following heat treatment program is recommended.

1. Hot isostatic pressing (HIP) in a shared cycle, with the

following parameters:

1200 C

1000 bar argon

240 minutes.

2. Homogenisation (HOM) heat treatment, with the following

parameters:

1220 C

0.70.9 mbar argon

240 minutes.

As rapid quench rate as possible, from 1220C to 760C in

8 minutes maximum. The purpose is to dissolve carbides

and improve the isotropy of the microstructure, reducing the

brittleness of the as-built EBM material.

Machining

Parts manufactured in the EBM process feature good machinability.

Parts produced using the Arcam EBM process

demonstrate excellent results when using any conventional

machining process.

The excellent properties displayed by the parts manufactured

with EBM allow polishing of the parts to a mirror or optical

finish for use in dies and other applications requiring a superior

surface finish

Microstructure

Manufacturing CoCr parts with EBM results in fully dense parts

without weld lines in the material before or after heat treatment

(HIP+HOM).

The as-built material consists of elongated grains containing

carbide precipitation. Heat treatment transforms the microstructure

into an isotropic structure with a substantial reduction

of visible carbides.

The images below show the typical microstructure before and

after heat treatment (HIP+HOM). The as-built material has elongated

grains in the build direction (Z). It contains a high density of

carbides that result the high hardness of the as-built material.

HIP+HOM completely transforms the microstructure into an

isotropic state. The carbides are dissolved, leading to the increased

ductility and reduced hardness demonstrated in the after

the heat treatment specifications. There is no porosity in the as

built or in the HIP+HOM material.

Arcam
 
© 2007-2011,  .
.
, , .13
(495) 380-05-15, abuniver@niit.ru
 —