Effect of WC grain size on mechanical properties and microstructures of cemented carbide with medium entropy alloy Co-Ni-Fe binder

For developing new binder phase with high performance, Co-Ni-Fe alloy was used as binder in cemented carbides. The mechanical properties of WC-CoNiFe and WC-Co cemented carbides with different grain sizes were studied. The results show that the reprecipitation of WC-CoNiFe is inhibited compared with that of WC-Co during sintering process, and the grains in WC-CoNiFe cemented carbides are more of smooth shape, resulting in a slightly lower hardness and higher transverse rupture strength. With the increase of the grain size, the hardness of the two cemented carbides decreases, and the transverse rupture strength increases. However, the slope values of K in Hall-Petch relationship are higher in WC-CoNiFe than those in WC-Co, indicating the high toughness of medium entropy alloy Co-Ni-Fe.

葡萄糖水热碳化催化热处理制备石墨微球

以葡萄糖为碳源、聚丙烯酸钠为分散剂、硝酸镍为催化剂的前驱体,采用水热碳化法一步制备了负载有Ni O催化剂的碳微球,再在氩气气氛下催化热处理制备了平均粒径约2μm的石墨化程度高、球形度及分散性好的石墨微球。研究了催化剂用量、热处理温度以及保温时间对合成石墨微球的影响。结果表明:当催化剂Ni的加入量为1.5%(质量分数)、热处理温度为1 200℃、保温时间为3 h时,所得石墨微球的石墨化程度最高。继续升高热处理温度或延长保温时间,石墨微球的石墨化程度反而降低,其原因可能是过高的温度或者过长的保温时间导致了催化剂的团聚及失活。碳微球的催化石墨化过程由溶解–析出机理决定。此外,石墨微球具有与鳞片石墨几乎相当的抗氧化性能,且远高于碳微球。