WC-Co tungsten carbide is an excellent material, which has a wide appliance. In the sintering process of WC-Co tungsten carbide, the fluctuation width of carbon content in the two phase (WC+γ) region is very narrow. At the same time, as the process out of control, the carbon deficiency of raw materials or the decarburization of the sintered medium will occur, making it difficult to obtain（WC+γ） two-phase alloys. 

 

 

The η phase that lack of carbon is one of the most common phase. η phase is a kind of malignant phase defects in the alloy, which makes the physical and mechanical properties of the alloy is very poor inferior. Based on this understanding, controlling the process conditions to avoid phase formation will become hard alloy manufacturing process must abide by the rules.

 

Usually, the η phase of the WC-Co tungsten carbide is in the form of single crystal grain, in which the amorphous WC grains are usually retained. The η phase can nucleate on the WC grain, can also produce the nuclear gamma phase, but essentially nucleation for WC gamma phase boundary. γ phase heap is not necessarily the ETA L phase preferred nucleation sites.

 

In WC-Co tungsten carbide, W diffuses from the WC grain to the γ phase slowly. As a result, the W concentration of WC- boundary is higher than that of the γ phase, and the nucleation is formed along the WC- phase boundary and with the WC grain surface as the heterogeneous core.

 

Generally speaking, in the micro phase conditions can show two kinds of state: block (figure a) and aggregation (figure b). Circular blunt boundary of point blocked η phase shows that η phase grew up along the γ phase (Co consumption) and dissolved (annex), while the WC grain expands. Clustered ETA phase boundary lacy has indicated that the phase of grain growth, the grain of WC was dissolved lag (Figure 3). The η phase can form characteristic patterns with regular geometric shapes.