Papers by Keyword: Die Material

Abstract: In recent, the development of new die materials is one of the important topics in the field of die research. In this paper, effects of nano-ZrO2 addition on the microstructure and mechanical properties of Ti(C,N)-based cermets were studied. The newly developed Ti(C,N)-based cermet die materials with different contents of nano-ZrO2 of 0~25wt% were prepared by hot pressing technique under vacuum atmosphere at 1450°C for 30min. Moreover, the microstructure of this Ti(C,N)-based cermet die materials was observed by environmental scanning electron microscope. It indicates that the comprehensive mechanical properties can reach the optimum when the weight percent of the nano-ZrO2 is 10%. The corresponding flexural strength and fracture toughness is 967 MPa and 13.62 MPa•m1/2, respectively which is approximately 65% and 110% higher than that of the cermet without nano-ZrO2 addition. It suggests that the addition of nano-ZrO2 can improve the mechanical properties especially the fracture toughness and flexural strength of Ti(C,N)-based cermet die materials.

Abstract: In this paper, back propagation neural network was used in the optimum design of the hot pressing parameters of an advanced ZrO2/TiB2/Al2O3 nanocomposite ceramic tool and die material. The BP algorithm could set up the relationship well between the hot pressing parameters and mechanical property of nanocomposite ceramic tool and die materials. After analyzed the predicted results, the best predicted results were the sintering temperature was 1420°C and the holding time was 60min. Under these hot pressing parameters, the best flexural strength and the best fracture toughness of the material could be obtained.

Abstract: In this paper, the two hybrid algorithms of back propagation artificial neural network and genetic algorithm were used in the optimum design of the hot pressing parameters of an advanced ZrO2/TiB2/Al2O3 nanocomposite ceramic tool and die material. Compared with the BP algorithm, the predicted results of hybrid algorithm indicated that the combination algorithm can offer a robust and efficient way for the fabrication process design of ceramic tool and die materials.

Abstract: Microstructures and mechanical properties of Ni3Al based intermetallic alloys produced by vacuum arc melting and vacuum induction melting were investigated in terms of phase analysis using scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffractometer and tensile test machine. The duplex microstructural feature consisting of γ’ matrix phase and small intermetallic dispersoids was observed to be distributed over the whole microstructure in the Zr and/or Mo-added samples. From the SEM-EDS analysis of the alloys, it is clearly confirmed that the Mo is solved both into γ’ matrix phase and intermetallic phase while Zr has a role to form an intermetallic Ni5Zr phase for the entire alloys investigated. The ultimate tensile strength of the present alloy was superior to iron-based and Ni-based die materials especially in the high temperature region. The mechanical results obtained will be discussed in correlation with microstructural observations, phase analyses.

Abstract: This study discusses electrochemical finishing of female screw using different types of completely inserted electrodes as well as feeding electrodes for die material. In the experiment, four types of design electrode are completely inserted and put through both continuous and pulse direct current and another four types of electrode are used with the application of continuous direct current and axial electrode feed. The controlled factors include the chemical composition and the concentration of the electrolyte, the electrolyte temperature, the flow rate of electrolyte, rotational speed of the electrode, current density, and current rating. The parameters are electrolytic time, die material, pulse period, feed rate of the electrode, and electrode geometry. For inserted electrodes, an electrode with thin plate provides more sufficient discharge space, which is advantageous for polishing. The electrode of single plate performs better than the double plate. Pulse direct current can promote the effect of electrochemical finishing, but the machining time is longer and the cost is raised. For feeding electrodes, an electrode of one side borer tip and thinner heavy section performs the best polishing effect in the current investigation. The electrochemical finishing after screw cutting just needs quite short time to make the surface of female screw smoothing and bright.

Abstract: The forging die material, a high strength steel designated W513 is considered in this paper. A fatigue damage model, based on thermodynamics and continuum damage mechanics, is constructed in which both the previous damage and the loading sequence are considered. The unknown material parameters in the model are identified from low cycle fatigue tests. Damage evolution under multi-level fatigue loading is investigated. The results show that the fatigue life is closely related to the loading sequence. The fatigue life of the materials with low fatigue loading first followed by high fatigue loading is longer than that for the reversed loading sequence.

Abstract: A conventional cast nickel-base superalloy with the chemical composition of Ni-16W-2Mo-1.5Cr-6Al wt % has been recently developed as isothermal forging die material operating at temperatures above 1000°C. The oxidation test results showed that the oxide scale spalled heavily after exposure in air at 1050°C for 100 h, which is unacceptable for the process of isothermal forging. To improve the high temperature oxidation resistance, 3 wt% Ta was added into the alloy. Specimens after oxidation test were analyzed by the scanning electron microscope (SEM) and the X-ray diffraction analysis (XRD). The results showed that the oxides were mainly NiO, NiWO4, and NiAl2O4 for all the samples. The oxidation resistance of the alloy with 3wt%Ta was fairly good at 1050°C with the mass gain rate of around 0.016g/m2•h and spallation of oxides less than 2g/m2 within 100h.The SEM results showed that a continuous protective layer of Al2O3 has been formed under the layer of NiO for the alloy containing Ta.