The tribological behavior of Al0.25 CoCrFeNi high-entropy alloy(HEA) sliding against Si3N4 ball was investigated from room temperature to 600°. The microstructure of the alloys was characterized by simple FCC pha...The tribological behavior of Al0.25 CoCrFeNi high-entropy alloy(HEA) sliding against Si3N4 ball was investigated from room temperature to 600°. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300°, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300°due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200°, then delamination wear and oxidative wear at 300°and became oxidative above 300°. Moreover, the adhesive wear existed concomitantly below 300°.展开更多
In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism o...In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force,was established.Three key factors have been taken into accounts in this model,such as the contact friction force between abrasive grains and materials,the plastic deformation of material in the process of abrasive plowing,and the shear strain effect of material during the process of cutting chips formation.The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel.Grinding force values of prediction and experiment were in good consistency.The errors of tangential grinding force and normal grinding force were 9.8%and 13.6%,respectively.The contributions of sliding force,plowing force and chip formation force were also analyzed.In addition,the tangential forces of sliding,plowing and chip formation are 14%,19%and 11%of the normal forces on average,respectively.The pro-posed grinding forcemodel is not only in favor of optimizing the grinding parameters and improving grinding efficiency,but also contributes to study some other grinding subjects(e.g.abrasive wheel wear,grinding heat,residual stress).展开更多
The abrasive wear behavior of high chromium cast iron （containing 12.9 mass% chromium） austenitized at 1 050 ℃ for 2 h and austempered in salt bath at 320 ℃ for 4 h was evaluated. Abrasive wear was performed using...The abrasive wear behavior of high chromium cast iron （containing 12.9 mass% chromium） austenitized at 1 050 ℃ for 2 h and austempered in salt bath at 320 ℃ for 4 h was evaluated. Abrasive wear was performed using alumina abrasive under four different loads, namely 50, 100, 150, and 200 N, for 36000 cycles. The worn surfaces and wear debris were analyzed by scanning electron microscopy, laser confocal microscopy and X-ray diffraction. Micro hard- ness profiles were also obtained in order to analyze the strain-hardening effects beneath the contact surfaces. Results indicate that the retained austenite in high chromium cast iron has experienced induced martensitic transformation af- ter tests, for small amounts of retained austenite could be detected by X-ray diffraction. In addition, there is a close relationship between wear mechanism and test load. Under the condition of lower test load, the wear mechanism is an uninterrupted and repeated process, during which matrix is cut at first and then fine carbides flake off. As to high- er test load, scratching and spalling induced by cleavage fracture of blocky carbide are the wear mechanism.展开更多
基金the opening project from National Key Laboratory for Remanufacturing (No. 61420050204)the Department of Energy (DOE), Office of Fossil Energy, National Energy Technology Laboratory (DE-FE-0011194), with Mr. V. Cedro, Mr. R. Dunst, and Dr. J. Mullen as program managers+1 种基金the support of the U.S. Army Research Office project (W911NF-13-1-0438) with the program manager, Dr. M. P. Bakas and Dr. D. M. Steppsupport from the National Science Foundation (DMR-1611180) with the program directors, Dr. G. J. Shiflet and D. Farkas
文摘The tribological behavior of Al0.25 CoCrFeNi high-entropy alloy(HEA) sliding against Si3N4 ball was investigated from room temperature to 600°. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300°, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300°due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200°, then delamination wear and oxidative wear at 300°and became oxidative above 300°. Moreover, the adhesive wear existed concomitantly below 300°.
基金financial support for this work by the National Natural Science Foundation of China(Nos.51775275,51921003 and 51905363)the Funding for Outstanding Doctoral Dissertation in NUAA of China(No.BCXJ19-06)+1 种基金the Natural Science Foundation of Jiangsu Province of China(No.BK20190940)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.19KJB460008)。
文摘In this article,a grinding force model,which is on the basis of cutting process of single abrasive grains combined with the method of theoretical derivation and empirical formula by analyzing the formation mechanism of grinding force,was established.Three key factors have been taken into accounts in this model,such as the contact friction force between abrasive grains and materials,the plastic deformation of material in the process of abrasive plowing,and the shear strain effect of material during the process of cutting chips formation.The model was finally validated by the orthogonal grinding experiment of powder metallurgy nickel-based superalloy FGH96 by using the electroplated CBN abrasive wheel.Grinding force values of prediction and experiment were in good consistency.The errors of tangential grinding force and normal grinding force were 9.8%and 13.6%,respectively.The contributions of sliding force,plowing force and chip formation force were also analyzed.In addition,the tangential forces of sliding,plowing and chip formation are 14%,19%and 11%of the normal forces on average,respectively.The pro-posed grinding forcemodel is not only in favor of optimizing the grinding parameters and improving grinding efficiency,but also contributes to study some other grinding subjects(e.g.abrasive wheel wear,grinding heat,residual stress).
文摘The abrasive wear behavior of high chromium cast iron （containing 12.9 mass% chromium） austenitized at 1 050 ℃ for 2 h and austempered in salt bath at 320 ℃ for 4 h was evaluated. Abrasive wear was performed using alumina abrasive under four different loads, namely 50, 100, 150, and 200 N, for 36000 cycles. The worn surfaces and wear debris were analyzed by scanning electron microscopy, laser confocal microscopy and X-ray diffraction. Micro hard- ness profiles were also obtained in order to analyze the strain-hardening effects beneath the contact surfaces. Results indicate that the retained austenite in high chromium cast iron has experienced induced martensitic transformation af- ter tests, for small amounts of retained austenite could be detected by X-ray diffraction. In addition, there is a close relationship between wear mechanism and test load. Under the condition of lower test load, the wear mechanism is an uninterrupted and repeated process, during which matrix is cut at first and then fine carbides flake off. As to high- er test load, scratching and spalling induced by cleavage fracture of blocky carbide are the wear mechanism.
