The Thermo-mechanical-corrosion Fatigue Behaviour Of Cemented Carbides

Cemented carbides,which are called industral tool,are indispensable tool and structural materials in modern industral and new technology field. In service, cemented carbides often need to suffer complex service conditions included cyclic stress, high temperature and corrosion. Fatigue is a main reason for the fracture of this kind of materials. The fatigue fracture is often caused by the combined effect of various fatigue mechanics. At present, the research on fatigue behaviour of cemented carbide is not enough, even less is the research on the fatigue behaviour under complex conditions, which is often the real case in the service.Four commercial grades cemented carbide YGH60、YGR60、YGH30、YGR30were the materials investigated in our work. The compressive deformation behaviour at room temperature and550℃as well as the thermo-mechanical-corrosion fatigue behaviour of cemented carbide had been investigated. The influence of temperature, binder content and composition on the compressive deformation behaviour had been discussed. In addition, the effect of pH value, binder content and composition on the thermo-mechanical-corrosion fatigue behaviour had also been discussed. The results are as follows:(1)The compression behaviour of cemented carbides at room temperature and550℃exhibit brittlely and without obvious yield point. The compression deformation can be devided into four stages which are corresponding to elastic deformation, fracture along WC grain boundaries, fracture along WC-binder interfaces and plastic deformation of binder phases respectively.(2)Temperature, binder content and composition affect the compressive deformation behaviour obviously:Compared with those at room temperature, both the elasticity modulus and the compression strength will decrease at550℃, while compression rate will increase. Increasing in binder content will lower the elasticity modulus and compression strength both at room temperature and at550℃, but will increase the compression rate. The influnce of binder composition on the elasticity modulus is more apparently in cemented carbides with higher binder content. As well, WC-CoNiCr alloys exhibit lower elasticity modulus and compression strength but higher compression rate than WC-Co alloys at both temperatures.(3)The influence of pH value on the thermo-mechanical-corrosion fatigue behaviour differs between WC-CoNiCr alloys and WC-Co alloys:Cooling media of acid liquor reduces the thermo-mechanical-corrosion fatigue life of WC-CoNiCr alloy more apparently than WC-Co alloy when compared with cooling media of neutral water. It seems that cooling media of neutral water and alkaline have the same effect on the thermo-mechanical-corrosion fatigue life of WC-CoNiCr alloy and WC-Co alloy.(4)The influence of binder content and composition on the thermo-mechanical-corrosion fatigue behaviour are as follows:WC-CoNiCr alloy YGR60exhibits better thermo-mechanical-corrosion fatigue bahaviour than that of the same binder content WC-Co alloy YGH60. WC-Co alloy YGH30alloy shows better thermo-mechanical-corrosion fatigue bahaviour than that of different binder content WC-Co alloy YGH60.