# Applications of Tungsten Pseudo-Alloys in the Energy Sector
## 2 Materials and Experimental Works  
As mentioned in the introduction, one way to increase the stored energy capacity is to change the flywheel material, either by increasing the strength of the flywheel to allow for an operation at higher allowable speeds or by simply increasing the mass while maintaining the original allowable speed.  
Tungsten pseudo-alloys are very heavy metal composite materials prepared via powder metallurgy. Some of them have exceptional mechanical properties. The basic component of the composite is tungsten, supplemented by small amounts of alloying elements, mainly cobalt, nickel, iron, and copper. The appropriate choice of alloys and the composition of the initial powder mixture determines, together with the technological process, the future mechanical properties of the material [10; 11; 12].  
From the set of W-MMC materials, high-strength W/Ni/Co or W/Ni/Fe/Co are particularly suitable for constructing the flywheel rotor. Their chemical composition is shown in Table 2.  
The manufacturing process of selected W-MMC composite materials is shown in Figure 1. It breaks down into three logical technological units--the moulding preparation node, the node of high-temperature metallurgical operations (sintering, quenching, annealing), and, in our case, the node of recycling of waste from chip machining.  
The input technological node involves the preparation/mixing of the initial powder mixture, either from primary original powders or from powders obtained through recycling, followed by filling the initial powder mixture into a suitably shaped vibrationally  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{5}{c}{**Chemical Composition (wt\%)**} & \multirow{2}{*}{**Density** (g/cm\({}^{-3}\))**} \\ \cline{2-2} \cline{4-6}  & **W** & **Ni** & **Fe** & **Co** & **(g/cm\({}^{-3}\))** \\ \hline TN & 91 & 6.0 & - & 3.0 & 17.45 \\ DS & 95.8 & 3.01 & 1.05 & 0.14 & 18.30 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical composition of W-MMC system materials and their density.  
compacted elastomeric mould. After filling, the mould is moulded in the compression chamber of an isostatic press. After removal of the mould from the isostatic press chamber, the finished product is obtained.  
The next technological node includes high-temperature and metallurgical processes. At first, the product (the pressed part) is placed in a suitable sintering furnace [13; 14] and, after sintering in a vacuum or protective atmosphere, annealed and quenched in water, cold or hot formed, and in the last step, aged through vacuum annealing. The sequence of operations and the characteristic temperature curves are shown in Figure 2. The heat treatment temperature curves may vary depending on the chemical composition of the composite materials.  
Figure 1: Technological scheme of production of W-MMC composite materials.  
Figure 2: Sequence of high-temperature technological operations during manufacturing of W-MMC composite materials. The purple squares indicate the individual technological steps.  
W-MMC composite materials can be divided into two basic groups based on the initial raw materials used. The first group consists of materials made from new powders. In contrast, the second group consists of materials made partially or entirely from recycled powders obtained by processing the materials of the first group.