Si < Sub > 3 < / Sub > N < Sub > 4 < / Sub > Base Preparation And Properties Of The Ceramic Research

White copper alloy extrusion die is a key component of extrusion equipment, because it suffered high temperatures and under pressure when working, it is easy to crack, collapse deformation. From the requirement for die materials, composite ceramic die materials with high mechanical properties were fabricated with composite method by selecting silicon nitride ceramics matrix which has excellent hardness, wear-resistance, high-temperature resistance and corrosion resistance materials. The strengthening and toughening mechanisms, microstructure, mechanical properties, friction and wear properties as well as thermal shock resistance of the ceramic die materials were investigated to provide technical basis for the application of ceramic materials.The flexural strength and fracture toughness of the two composite ceramic materials are1130MPa,12MPa·m1/2and840MPa,9.4MPa·m1/2respectively. The phase and microstructure of two kind of ceramic samples were analyzed by XRD, SEM and TEM.Both of them contain a lots of long columnar beta Si3N4grains which uniform distribution for sample1,and there is particle Ti(C, N) agglomeration for sample2.Because of this,the fracture behavior of sample1is mostly inter-granular fracture and beta Si3N4grains pull out,not trans-granular fracture for sample2.Both of silicon nitride ceramics performed the mix mode of thermal shock facture and thermal shock damage. The critical thermal shock temperature of the two samples are750K and650K, respectively, which because of better flexural strength and fracture toughness of sample1.The hardness enhancement and optimization of structure lead to the improvement of wear resistance of Si3N4mold material. The two materials proved the same trend, the friction coefficient decreases with the increases of load and increased with the increases of time; the wear rate increases with the increases of load and increased with the increases of time.The two Si3N4ceramic die materials main friction mechanism were abrasive wear, adhesive wear, fatigue wear. The main friction mechanism change from abrasive wear at initial stage to adhesive wear with temperatures rise of wear surface, and there is always fatigue wear while all procedures.