1.Selection and properties of preform materials
The mass fraction of ZrO2 in ztap is 40wt%, the particle size is 1 ~ 2mm, and some physical / mechanical properties are obtained. The particle size of the high chromium alloy powder is 50 ~ 100 μ m, and the chemical composition is high.
2.Preparation of ztap / HCCI composite
Ztap, high chromium alloy powder and self-made binder were mixed evenly in a certain proportion, and then pressed and dried in a grid mold. The demoulded ceramic preform was sintered in a vacuum furnace at 1150 ℃ for 2 h to obtain a honeycomb preform. The preform was fixed in the casting cavity, HCCI liquid, HCCI chemical composition, pouring temperature of 1450 ~ 1465 ℃, cooling to obtain ztap / HCCI composite.
3.Analytical characterization and performance testing
The composite material was cut with resin grinding wheel and the sample was pre ground with a grinder. The samples were roughly and finely ground with four kinds of metallographic sandpaper of 180 mm, 400 mm, 1000 mm and 2000 mm, polished with polishing cloth and corroded with 4% nitric acid alcohol solution for 30s. The metallographic structure of the matrix was analyzed by 4xc-pc optical microscope, jsm-6510 scanning electron microscope and Ultima IV X-ray diffractometer
The element distribution and phase composition in the bonding zone of ceramics were studied.
The wear resistance was tested by mmh-5 three body abrasive wear tester manufactured by Jinan Hansen Precision Instrument Co., Ltd. The rotation speed of the spindle is 30R / min, the load is 3kg, the abrasive is quartz sand, the hardness is hv1000-1200, and the particle size is 150-250 μ M. The wear sample is perpendicular to the honeycomb structure, so that the area fraction of ceramic particles on the worn surface of the sample remains unchanged during the three body wear test. The principle of three body abrasive wear test and the sample are shown in Fig. 1. After 15 min pre grinding, the initial mass was obtained by weighing. The wear test was carried out for 8 grinding passes, each of which lasted for 60 min. at the end of each grinding process, the samples were cleaned, dried and weighed.
Because the density of metal and ceramic is different, the wear resistance of composite can not be evaluated by weight loss
⻍ L is the volume loss of the composite;
⻔ L is the weight loss of composite materials;
𝜌 is the density of composite material;
𝜑 is the volume fraction of ceramic;
𝜌 C is the density of ZTA ceramics;
𝜌 m is HCCI density.