MWCNTs Enhanced Cemented Carbide And Its Properties

Cemented carbides are often praised as "industrial teeth" for their high hardness and strength.With the development of materials science,the mechanical properties of cemented carbides,which are often used as cutting tools,are required more strictly.Especially in the process of practical application,the hardness and toughness of the material are required to be of high standard.Otherwise,it is easy to break down or make it fail.As the result,it is necessary for cemented carbide with toughness and hardness to achieve high mechanical properties.A lot of research results have proved that the CNT is a kind of strengthening phase with infinite prospect.However,the dispersion of CNTs often determines its strengthening effect in the matrix.If the CNTs are poorly dispersed,the mechanical properties of the sample will be seriously deteriorated.Therefore,it is particularly important to be able to prepare materials in which CNTs are uniformly dispersed.In this study,cemented carbide powders with CNTs as reinforcing phase were prepared by in-situ growth method in this experiment.Finally,cemented carbide blocks were prepared by spark plasma sintering(SPS)and their properties were tested and analyzed.Firstly,all the composite powders were prepared by carbothermal reduction in situ using oxides as raw materials.According to XRD patterns,when the carbon source is enough,the WC-Co-CNTs powder without impurity phase can be prepared.There is a large amount of CNTs in the powder,and there is no agglomeration phenomenon can be seen from SEM observation results.However,amorphous carbon exists in the powder,which worsens the comprehensive mechanical properties of the celented carbides.Therefore,the process still needs to be further studied.Secondly,CNTs were in situ prepared on the surface of WC matrix by polymer pyrolysis with WC as tungsten source,and WC-Co-CNTs composite powder was obtained by mechanical alloying.The effects of different atmosphere conditions and carbon source content on the growth of CNTs were discussed.The hardness of the final cemented carbide blocks fluctuates in the range of 83.1?85.96 HRA.Finally,Al2O3 powders were prepared by chemical precipitation method and coated with dispersed CNTs.The CNTs was uniformly dispersed and had a good interface with alumina.Finally,WC-CNTs@Al2O3 composite powders were obtained by mechanical alloying.When the content of CNTs is 1.6 wt%,cemented carbide has the best mechanical properties by comparing the cemented carbide containing different CNTs,and the hardness of cemented carbide is increased by 44.4%(27.14 GPa)compared with the cemented carbide without adding CNTs,and the fracture toughness increased by 31.30%(12.35 MPa·m1/2).