Preparation And Organization Of The .wc/al203-cr-mo-ni Metal Ceramics, Mechanical Properties

White copper alloy extrusion die is a key component of extrusion equipment,it suffered high temperatures and under pressure when working,and the wear resistance of metal ceramic, red hardness and toughness is not enough, and easy to crack,collapse deformation. From the requirement for die materials,multi-phase composite ceramic die materials with high mechanical properties were fabricated successfully with multi-phase composite method. The correlations among the material composition,the hot pressing process, the microstructures, mechanical properties and thermal shock resistance were investigated. The strengthening and toughening mechanisms of the multi-phase composite ceramic die materials were studied systematically.The elemental powders and the composite powders were fabricated by planet ball-milling,we have achieved the fine and uniformly powders,it is benefit to subsequently hot-pressed sintering. The effects of WC,Al2O3 and metal Ni on the microstructure and mechanical properties of multi-phase composite ceramic die materials were discussed. The hot press sintering parameters were optimized. WC/Al2O3-Cr-Mo-Ni composite ceramic composite ceramic die material was fabricated successfully. Result shows that excellent mechnical property and microstructure could be obtained only with the condition of the suitable volume fraction and the suitable HP sintering technique. With increasing Ni additions,the flexural strength and fracture toughness of the composites increased,while the hardness is decreased,with increasing Al2O3 content,the change of the mechnical property of the composite is opposited to that the addition of Ni content.WC/Al2O3-Cr-Mo-Ni composite ceramic have been developed successfully by hot-pressed at 1500℃under 25 MPa in flowing argon. A flexural strength of 567MPa, a fracture toughness of 7.46 MPa·m1/2 and a Vicker's hardness of 15.24GPa are obtained with the addition of 7wt.% Ni and 10wt.% Al2O3 microparticles. The mechnical perporty of the same component prepared by HIP sintering is superior to than of hot-pressed sample, its flexural strength, fracture toughness and Vicker's hardness are 623MPa,7.75MPa·m1/2 and 15.98GPa,respectively. The fracture surface of the composite was characterized by a mix of intergranular and transgranular fracture as a result of the presence of both intergranular and intragranular secondary phase particles due to the increasing of Ni content. Toughening mechanisms of multiple reinforced WC/Al2O3-Cr-Mo-Ni cermets were studied. The main toughening mechanisms are fine grain strengthening and toughening,intergranular toughneing,crack deflection,crack bridging,crack branching toughening. It is suggested that theincrement in the mechanical properties of muiti-phase reinforced WC/Al2O3-Cr-Mo-Ni ceramics is due to the combined effects of toughening mechanisms. Finally,the thermal shock resistance of composite was also studied, The critical temperature difference(△Tc) was 260～280K,higher 80K than that of monolith. Fined grains and multiphase improve the thermal shock resistance of the composites.