A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 ℃ and initial stress level of 250 MPa.Based on the experimental stress relaxation curve,the relationship between creep strain ra...A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 ℃ and initial stress level of 250 MPa.Based on the experimental stress relaxation curve,the relationship between creep strain rate and stress has been derived.Then,a set of creep constitutive equations has been built and the values of constants arising in the constitutive equations have been determined by fitting the creep strain rate-stress curve.Close agreement between computed results and experimental ones is obtained for stress relaxation data.The creep constitutive equation set has been integrated with the commercial FE(finite element) solver MSC.Marc via the user defined subroutine,CRPLAW,for the vacuum hot bulge forming process modelling of Hastelloy C-276 thin-walled cylindrical workpiece.The temperature field,the radius-direction displacement field and the stress-strain field are calculated and analyzed.Furthermore,the bulging dimension and the final internal diameter of workpiece are predicted and the test results verify the reliability of the finite element method.展开更多
C-276 nickel-based alloy is a difficult-to-cut material. In high-speed machining of Hastelloy C-276, notching is a prominent failure mode due to high mechanical properties of work piece, which results in the short too...C-276 nickel-based alloy is a difficult-to-cut material. In high-speed machining of Hastelloy C-276, notching is a prominent failure mode due to high mechanical properties of work piece, which results in the short tool life and low productivity. In this paper, a newly developed Ti(C7N3)-based cermet insert manufactured by a hot-pressing method is used to machine the C-276 nickel-based alloy, and its cutting performances are studied. Based on orthogonal experiment method, the influence of cutting parameters on tool life, material removal rates and surface roughness are investigated. Experimental research results indicate that the optimal cutting condition is a cutting speed of 50 m/min, depth of cut of 0.4 mm and feed rate of 0.15 mm/r if the tool life and material removal rates are considered comprehensively. In this case, the tool life is 32 min and material removal rates are 3000 mm3/min, which is appropriate to the rough machining. If the tool life and surface roughness are considered, the better cutting condition is a cutting speed of 75 m/min, depth of cut of 0.6 mm and feed rate of 0.1 mm/r. In this case, the surface roughness is 0.59μm. Notch wear, flank wear, chipping at the tool nose, built-up edge(BUE) and micro-cracks are found when Ti(C7N3)-based cermet insert turned Hastelloy C-276. Oxidation, adhesive, abrasive and diffusion are the wear mechanisms, which can be investigated by the observations of scanning electron microscope and energy-dispersive spectroscopy. This research will help to guide studies on the evaluation of machining parameters to further advance the productivity of nickel based alloy Hastelloy C-276 machining.展开更多
基金Project(2009CB724307)supported by the Major State Basic Research Development Program(973 Program)of China
文摘A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 ℃ and initial stress level of 250 MPa.Based on the experimental stress relaxation curve,the relationship between creep strain rate and stress has been derived.Then,a set of creep constitutive equations has been built and the values of constants arising in the constitutive equations have been determined by fitting the creep strain rate-stress curve.Close agreement between computed results and experimental ones is obtained for stress relaxation data.The creep constitutive equation set has been integrated with the commercial FE(finite element) solver MSC.Marc via the user defined subroutine,CRPLAW,for the vacuum hot bulge forming process modelling of Hastelloy C-276 thin-walled cylindrical workpiece.The temperature field,the radius-direction displacement field and the stress-strain field are calculated and analyzed.Furthermore,the bulging dimension and the final internal diameter of workpiece are predicted and the test results verify the reliability of the finite element method.
基金Supported by Program for New Century Excellent Talents in University of China(Grant No.NCET-13-0357)Shandong Provincial Natural Science Foundation of China(Grant No.ZR2014EEM026)Tai Shan Scholar Foundation of China
文摘C-276 nickel-based alloy is a difficult-to-cut material. In high-speed machining of Hastelloy C-276, notching is a prominent failure mode due to high mechanical properties of work piece, which results in the short tool life and low productivity. In this paper, a newly developed Ti(C7N3)-based cermet insert manufactured by a hot-pressing method is used to machine the C-276 nickel-based alloy, and its cutting performances are studied. Based on orthogonal experiment method, the influence of cutting parameters on tool life, material removal rates and surface roughness are investigated. Experimental research results indicate that the optimal cutting condition is a cutting speed of 50 m/min, depth of cut of 0.4 mm and feed rate of 0.15 mm/r if the tool life and material removal rates are considered comprehensively. In this case, the tool life is 32 min and material removal rates are 3000 mm3/min, which is appropriate to the rough machining. If the tool life and surface roughness are considered, the better cutting condition is a cutting speed of 75 m/min, depth of cut of 0.6 mm and feed rate of 0.1 mm/r. In this case, the surface roughness is 0.59μm. Notch wear, flank wear, chipping at the tool nose, built-up edge(BUE) and micro-cracks are found when Ti(C7N3)-based cermet insert turned Hastelloy C-276. Oxidation, adhesive, abrasive and diffusion are the wear mechanisms, which can be investigated by the observations of scanning electron microscope and energy-dispersive spectroscopy. This research will help to guide studies on the evaluation of machining parameters to further advance the productivity of nickel based alloy Hastelloy C-276 machining.
