Metal injection moulding of a new Fe-8Ni micron-size pre-alloyed powder
Technical Paper: PIM International, Vol.3 No. 4 December 2009, pages 54-59, 2107 words
Eurotungstene, 9 rue André Sibellas, BP 152X, 38042
With more than 60 years of international experience in powder metallurgy, Eurotungstene operates in business sectors such as cemented carbides, high-density materials, diamond tools and recently also in the metal injection moulding (MIM) industry as a manufacturer of micron-size metal powders.
Eurotungstene’s ability to innovate in the diamond tools industry has allowed the company to be considered as a technological leader: the company was the first to develop a new concept in binders for diamond tools applications (1997), and to produce, on an industrial scale, an extensive range of pre-alloyed powders by hydrogen reduction. This innovative solution  aims to replace the use of cobalt in binders for diamond tools: the more competitive pre-alloyed powders are now largely consumed by tool manufacturers.
Today, Eurotungstene offers its know-how and its experience to the MIM industry. By making a pre-alloyed Fe-8Ni powder, PA-FN08, with enhanced sintered part properties, Eurotungstene’s manufacturing process allows us to consider an alternative to the atomised or blended carbonyl powders [2-5]. PA-FN08 belongs to Microneex®, a range of micron-size metal powders, specially designed for MIM applications. PA-FN08 is the first pre-alloyed powder developed for the MIM industry by this manufacturing process that Eurotungstene is extending to other grades (Fe-36Ni, Fe-50Ni, Fe-29Ni-17Co…).
Part I. Development of a micron-size MIM powder
Considering the MIM market requirements and the µ-MIM developments, the aim of this research was to tailor a micron-size Fe-8Ni powder, suitable for the MIM process  and providing good mechanical properties [7-11]. A description of the study and key parameters of the Fe-8Ni powder are provided, followed by the characterisation of the final commercial PA-FN08 powder and mechanical properties of a sintered specimen in Part II.
Experimental material and procedure
Eurotungstene produced four micron-size pre-alloyed Fe-8Ni powders through different processes. Powder properties displayed in Table 1 show different tap densities. Powder aspects are illustrated in the SEM pictures (Fig. 1). Oxygen levels were quite high but linked to a non-industrial process.
Binder system and mixing
In order to evaluate the compounding ability of the powders, four feedstocks were prepared: the four references of powders were mixed in a standard polymer-wax feedstock. Its composition was 54wt% polypropylene (PP), 43wt% paraffin wax (PW), 3wt% stearic acid (SA).
The mixing operations were conducted in a Brabender Plastograph W50EHT mixer with a pair of roller rotor cylinders, which is giving torque as a function of time. Homogeneity and maximum solid loading of each feedstock were evaluated by torque measurements [12-13] .
The same procedure was repeated for four tests: a small amount of powder was added, about 10g, all within two minutes, in order to wait for feedstock homogenisation. Depending on the powder and the binder, stabilisation sometimes proved difficult to obtain. However, a clear progressive increase trend of the torque was observed. A steady state value of the torque between two additions is a representation of homogeneity of the feedstock. The critical solid loading (in vol%) was considered to be reached when the torque curve displayed a drastic increase with the addition of a small amount of powder. In a second step, several tests were conducted with different ratios of paraffin wax. Stearic acid content was fixed for all four experiments, at a constant temperature of 180°C....
Further sections of this paper include:
- Part I. Development of a micron-size MIM powder
- Experimental material and procedure
- Powder characterisation
- Binder system and mixing
- Results and discussion
- Behaviour of powders in the feedstocks
- Tap density as criterion for MIM powders
- Ability of Powder 3 to be held in different binder systems
- Part II. Complete evaluation of PA-FN08
- PA-FN08 technical characteristics
- F-FN08 feedstock preparation and injection moulding
- Debinding and sintering conditions
- Results and discussion
- Green parts
- Sintered parts
- Mechanical properties
- Microstructure evaluation
Figures and Tables:
Table 8 Comparison of porosity