Proposal for change of compound carbide grade

       In the past, the alloy grades used by manufacturers to produce this product were YG8 or YG6. Later, due to fierce competition, in order to reduce costs, the YG type was changed to the YT type on the premise that the basic properties of the alloy can be met. According to the different characteristics of WC and TiC and the wetting effect of cobalt on the two, it can be judged that the hardness, red hardness, and fatigue resistance of the changed alloy will be improved, and its strength, wear resistance and impact resistance will be reduced. Therefore, how to maximize the strength and impact resistance of the modified alloy is particularly important.

    1. We know that the maximum saturated solubility of WC in TiC is 70% at an alloy sintering temperature of about 1400 degrees. If CK32 is used, since WC has not reached saturation dissolution, some WC will still dissolve into TiC during the sintering process of the alloy. In the normal sintering temperature and sintering time of the alloy, and with cobalt barrier, WC cannot be completely saturated and dissolved in TiC, and a brittle blue ring structure will be produced. The formation of the ring structure will appropriately improve the wear resistance of the alloy, but will greatly reduce the impact toughness of the alloy. Therefore, I suggest that CK24 solid solution should be used. Because CK24 is at a temperature of more than 2200 degrees, completely saturated WC dissolved in TiC. Therefore, at the sintering temperature of the alloy, WC will no longer be dissolved in TiC, and brittle substances will not be produced.

    2. The subcrystalline size of CK24 can reach 3100 angstroms, which is much larger than the 1500 angstroms of CK32. Obviously, the stability of the alloy produced by CK24 is much stronger than that of CK32. In addition, under the same formula and process, the WC grain size of the alloy produced with CK24 is also the largest, thereby enhancing the impact resistance of the alloy.

    3. Why choose slightly oversaturated CK24? As mentioned earlier, the saturated solubility of WC in TiC is 70%, but this refers to the case at about 1400 degrees. At a sintering temperature of about 2200 degrees for CK, its saturated solubility is greater than 70%. Therefore, in order to make the solid solution structure absolutely full and balanced, it is necessary to appropriately increase the content of WC in the solid solution when producing CK materials. In addition, since the slightly supersaturated solid solution is used, during the alloy sintering process, more coarse-grained WC will accumulate around the solid solution. This also helps to improve the impact resistance of the alloy.

    Fourth, after changing the grade, the points should be noted: 1. Pay special attention to the particle size matching of solid solution and WC. Because after CK24 is selected, the solid solution particle size is relatively stable during the alloy firing process and will not become finer due to the inward dissolution of WC. Therefore, WC that is slightly thicker than in the past may be used in alloy batching. Make the solid solution particle size slightly larger than the WC particle size, and the difference between the two should not be too large; 2. When configuring the alloy mixture, try to make the hard phase saturated with carbon. If the process needs to reduce the total carbon, it can only be solved by reducing the total carbon in the solid solution, so as to avoid the production of more highly brittle substances W2C due to the reduction of the total carbon in WC.