造孔剂对金属结合剂金刚石磨具力学性能的影响

Effect of pore-forming agents on mechanical properties of metal-bonded diamond wheels

磨具中具有适量的孔隙可在磨削过程中起到排屑、冷却和促使磨具自锐的作用。由于金属结合剂磨具的烧结密度高,对金刚石的把持力较高,所以在磨削过程中磨具的自锐性较差。本文利用真空热压烧结法,在相同的试验工艺条件下,通过添加不同含量的造孔剂NaC l、K3PO4和CO(NH2)2,详细对比和分析了造孔剂种类与用量对金属结合剂抗折强度与硬度的影响。通过实验发现:造孔剂的粉末形状、造孔剂与金属结合剂的密度差都对结合剂的力学性能有直接的影响。造孔剂原料形状越规则,试样中孔的形状就越规则,对试样强度和硬度下降的影响越小;造孔剂含量越多,因孔含量随之增加,强度与硬度都会下降;NaC l较好的颗粒形状对称性以及在热压过程中不易变形的特性保证了试样中较好的孔形和对称性,它对结合剂力学性能影响明显优于造孔剂K3PO4和CO(NH2)2。

Having an amount of holes in abrasive wheels is helpful to chip escaping, cooling and self- sharpening during grinding. Metal bond diamond wheels have lower diamond self-sharpening capability because of higher sintering density and high holding force to diamond grains. In the research, the authors studied the change of bending strength and hardness of the samples along with the amount of pore-forming agents including NaCl, K3 PO4 and CO （NH2）2. All experiments were made under the same technological parameters with vacuum hot pressing sintering machine. The experimental results showed that the better round the pore-forming agent＇ s shape, the higher degree of sphericity of the holes and the less decrement of the bending strength and hardness. The bending strength and hardness decrease with the increase of the amount of pore-forming agents. Because NaCl has good particle shape and non-deformability during hot-pressing, the shape of holes holds up well in the samples, and the mechanical property of samples with NaCl agent is obviously better than with KaPO4 or CO（NH2）2.