Effect of different granulation processes and powder particle sizes on uniformity of diamond distribution in the mixed powder

ObjectivesWith the rapid development of diamond tool quality and varieties, the requirements for diamond tool properties are increasingly rigorous, and the uniformity of diamond distribution in diamond tools is an important index affecting its performance. The imperfect granulation process of mixed powder containing diamond is one of the reasons for the uneven distribution of diamond in diamond tools. By studying the secondary particle morphology obtained by different granulation processes and the influence of mixed powder with different particle sizes on the uniform distribution of diamond, the distribution uniformity of diamond in the mixed powder is improved, so as to improve the performance of diamond tools.MethodsUsing the same premixed powder as raw material, three different granulation processes—disk granulation, cold press crushing granulation, and diffusion crushing granulation—were used to carry out experiments. The powders of the three granulation processes were sieved using stainless steel standard sieves, and the particle size samples of 180 to 380 μm, 120 to 180 μm, and 75 to 120 μm were obtained under the same process. The effects of different granulation processes and different powder particle sizes on the distribution of 250 to 380 μm diamond in the same mixed powder were studied. At the same time, the nine-point sampling method was used to sample. The actual numbers of diamond particles in each sample were counted manually, the actual numbers of particles were compared with the calculated theoretical numbers of diamond particles and the deviation values were obtained. The averages and the ranges of the deviation values were used to determine the uniformity of diamond distribution in the mixed powder containing diamond.Results(1) From the morphology of the powder particles, it can be seen that the circular granulation produces spherical-shaped powder, the cold press crushing granulation produces irregularly shaped powder with distinguishable original particle morphology on its surface, and the diffusion crushing granulation produces irregularly complex shaped powder. (2) The loose packing ratio of powder produced by cold press crushing granulation is the highest, while the loose packing ratio of powder produced by disk granulation and diffusion crushing granulation is not significantly different. Under the same granulation process, the loose packing ratio of large particles is smaller, but as the particle size decreases, the influence of particle size becomes smaller. The flow rate of disk granulation is the highest and decreases with the decrease of particle size, but the flow rate of cold press crushing granulation is the lowest and the change is not significant, while the flow rate of diffusion crushing granulation is in the middle. (3) Under the same granulation process conditions, the distribution uniformity of diamond in mixed powder samples of 180 to 380 μm with three different granulation processes is the best. Under the same particle size range conditions, the distribution uniformity of diamond is the best in the mixed powder samples which are all diffusion crushing granulation. Compared with the diamond distribution in the different particle size mixed powder of the three methods of granulation process, the distribution of diamond controlled in the particle size interval of 180 to 380 μm by diffusion granulation process is the best.ConclusionsThe influences of the same kind of premixed powder on the distribution of diamond in the mixed powders under different granulation process conditions and different particle sizes is studied, and the following conclusions are drawn: (1) The particle morphology of different granulation processes is different. The powder particle morphology of disk granulation is a pseudo-spherical shape like "potato", the powder particle morphology of cold press crushing granulation is irregular shape and the surface can distinguish the original particle morphology, and the powder particle morphology of diffusion crushing granulation is complex irregular shape. (2) Under the same granulation process conditions, the distribution uniformity of diamond in the mixed powder with particle size of 180 to 380 μm (original particle size of 250 to 380 μm) is obviously better than that of the mixed powders with particle size of 120 to 180 μm and 75 to 120 μm. (3) Under the condition of the same particle size range, the distribution uniformity of diamond in the mixed powder under the diffusion crushing granulation is obviously better than that under the disk granulation process and the cold press crushing granulation process.