The influence of mischmetal （Ce-La） addition on phase transformation and as-cast microstructure characteristics of M2 high-speed steel （HSS） was investigated using Thermo-Calc software, differential scanning calor...The influence of mischmetal （Ce-La） addition on phase transformation and as-cast microstructure characteristics of M2 high-speed steel （HSS） was investigated using Thermo-Calc software, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy with energy dispersive spectrometry. The results showed that the measured phase transition points of M2 HSS were broadly consistent with the theoretical results. After mischmetal addition, the liquidus peak temperature, the peak temperature of the eutectic precipitation of M6C and MC were all increased, especially for the M6C which was affected significantly and increased about 31 °C. The contents of Mo and V in the eutectic carbide decreased and that of Fe increased, while in the matrix, the Mo, V and Cr contents all increased slightly. Furthermore, the microstructure of as-cast dendrite and ledeburite were refined, the total eutectic carbide content decreased and distributed into a discontinuous network, the lamellar spacing of M2C was reduced and the lamellae became thinner.展开更多
M2高速钢是使用最广泛和最具代表性的工具钢。采用电子束选区熔化(selective electron beam melting,SEBM)增材制造技术成形M2高速钢能有效避免传统铸造组织粗大、碳化物偏析等问题,有望大幅改善高速钢力学、磨损等性能。通过使用不同...M2高速钢是使用最广泛和最具代表性的工具钢。采用电子束选区熔化(selective electron beam melting,SEBM)增材制造技术成形M2高速钢能有效避免传统铸造组织粗大、碳化物偏析等问题,有望大幅改善高速钢力学、磨损等性能。通过使用不同扫描参数与2种粉床预热温度在316L不锈钢基板上制备了M2高速钢块体试样,重点研究了扫描参数和粉床预热温度对成形M2高速钢致密度及晶粒尺寸、碳化物等显微组织的影响。在最优化参数下,成形M2高速钢致密度达99.7%,平均晶粒尺寸在3~6μm,碳化物细小且分布较为均匀。通过维氏硬度试验和摩擦磨损试验分析了SEBM成形M2高速钢的硬度与磨损性能。结果表明,在最优化参数下成形的M2高速钢维氏硬度可达1034.2HV_(0.2),远高于商用M2高速钢刀具(815HV_(0.2)~845HV_(0.2)),同时磨损率仅有(3.58±0.36)×10^(-5)mm^(3)·N^(-1)·m^(-1),较回火态锻造母材降低了13.7%。此外,SEBM成形M2高速钢的磨损机制主要为磨粒磨损和粘着磨损。展开更多
The influence of Ce on the solidification microstructures of M2 high speed steel was studied. The results show that Ce has the effect of alleviating the segregation of alloying elements such as W and Mo in high speed ...The influence of Ce on the solidification microstructures of M2 high speed steel was studied. The results show that Ce has the effect of alleviating the segregation of alloying elements such as W and Mo in high speed steel. With the addition of Ce, the amount of eutectic carbides is decreased and the flakes of the carbides are refined. Ce mainly segregates onto the interface between the eutectic carbide and austenite, and a Dart of Ce enters M2C carbide. Ce can also enhance the breaking and spheroidizing of the network eutectic carbides during high temperature heat treatment.展开更多
Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites ...Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites grow into the melt and then the fine equiaxed cellularstructure appears in upper melt region nearly surface.The substructure of cellular grains anddendrites was observed to consist of martensite and retained austenile,while the carbides asM_6C_■ Cr_7C_3 and MC distributed at their boundaries.It is believed that the highermicrohardness up to HV_(0.1)=865-960 of the laser fused structure of the alloy is due to the oc-currence of martensite.展开更多
Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accum...Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accumulation of lubricant in front of patterned islandic spots creates thrusting to mating part and subsequently reduces contact between the mating couple. Whilst wear debris is likely to be spun off the plateau of the spots to their neighbouring valleys so as to reduce wear. Hence, it gives favorable tribological characteristics. Aiming at verifying such mechanisms, studies were performed on M2 steel disc specimens slid with ASSAB 17 tool steel pin. The M2 steel disc specimens were respectively （i） machined with non-patterned （NP）, （ii） etched to produce in-lined （INE） islandic patterns, and （iii） etched to produce staggered （STE） islandic spot patterns. Results indicated that the INE patterned discs gave most favorable wear characteristics, the NP of the worse characteristics whilst the STE ranged in the middle. However, the actual contact mechanism leads to the descending sequence of favorable friction behaviors nominally as： NP, INE and STE.展开更多
The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic ...The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate, the characteristics of current response was mainly relative tp the process of new surface repassivation.The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate展开更多
在实验室条件下采用立式连铸的方法连铸φ100 mm M2钢,在扫描电镜下观察分析其碳化物的分布、形貌、尺寸和类型,研究了析出碳化物的演变规律,并对其在液相区、固-液两相区和固相区的析出规律进行了热力学计算。结果表明:φ100 mm M2钢...在实验室条件下采用立式连铸的方法连铸φ100 mm M2钢,在扫描电镜下观察分析其碳化物的分布、形貌、尺寸和类型,研究了析出碳化物的演变规律,并对其在液相区、固-液两相区和固相区的析出规律进行了热力学计算。结果表明:φ100 mm M2钢连铸坯碳化物呈网状分布,网状碳化物的厚度从铸坯边部的1.5μm增大到中心的30μm,增大约20倍。碳化物形貌包括:块状、片层状和棒状,其中块状碳化物为VC,而片层状和棒状碳化物为M_2C。在液相和固-液两相区δ铁素体析出过程中,各种碳化物均不具备析出的热力学条件;在固-液两相区中γ奥氏体转变过程中,W_2C在1504 K具有析出的热力学条件;当温度降到固相线以下时,碳化物的析出顺序为VC>Mo_2C>W_2C,其析出温度分别为1475 K、549 K和333 K。展开更多
基金supported by National Natural Science Foundation of China(51171161,51101137)the Major Projects of the State Nuclear Power(2011ZX06004-016)Science Fund for Distinguished Young Scholars in Hebei Province(E2011203131)
文摘The influence of mischmetal （Ce-La） addition on phase transformation and as-cast microstructure characteristics of M2 high-speed steel （HSS） was investigated using Thermo-Calc software, differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy with energy dispersive spectrometry. The results showed that the measured phase transition points of M2 HSS were broadly consistent with the theoretical results. After mischmetal addition, the liquidus peak temperature, the peak temperature of the eutectic precipitation of M6C and MC were all increased, especially for the M6C which was affected significantly and increased about 31 °C. The contents of Mo and V in the eutectic carbide decreased and that of Fe increased, while in the matrix, the Mo, V and Cr contents all increased slightly. Furthermore, the microstructure of as-cast dendrite and ledeburite were refined, the total eutectic carbide content decreased and distributed into a discontinuous network, the lamellar spacing of M2C was reduced and the lamellae became thinner.
文摘M2高速钢是使用最广泛和最具代表性的工具钢。采用电子束选区熔化(selective electron beam melting,SEBM)增材制造技术成形M2高速钢能有效避免传统铸造组织粗大、碳化物偏析等问题,有望大幅改善高速钢力学、磨损等性能。通过使用不同扫描参数与2种粉床预热温度在316L不锈钢基板上制备了M2高速钢块体试样,重点研究了扫描参数和粉床预热温度对成形M2高速钢致密度及晶粒尺寸、碳化物等显微组织的影响。在最优化参数下,成形M2高速钢致密度达99.7%,平均晶粒尺寸在3~6μm,碳化物细小且分布较为均匀。通过维氏硬度试验和摩擦磨损试验分析了SEBM成形M2高速钢的硬度与磨损性能。结果表明,在最优化参数下成形的M2高速钢维氏硬度可达1034.2HV_(0.2),远高于商用M2高速钢刀具(815HV_(0.2)~845HV_(0.2)),同时磨损率仅有(3.58±0.36)×10^(-5)mm^(3)·N^(-1)·m^(-1),较回火态锻造母材降低了13.7%。此外,SEBM成形M2高速钢的磨损机制主要为磨粒磨损和粘着磨损。
文摘The influence of Ce on the solidification microstructures of M2 high speed steel was studied. The results show that Ce has the effect of alleviating the segregation of alloying elements such as W and Mo in high speed steel. With the addition of Ce, the amount of eutectic carbides is decreased and the flakes of the carbides are refined. Ce mainly segregates onto the interface between the eutectic carbide and austenite, and a Dart of Ce enters M2C carbide. Ce can also enhance the breaking and spheroidizing of the network eutectic carbides during high temperature heat treatment.
文摘Microstructure of the deepest zone of high speed steel W6Mo5Cr4V2(M2)melt after laser fu-sion was found to be so fine as the ehill zone of a solidified ingot.When narrower chill zoneformed,the long columnar dendrites grow into the melt and then the fine equiaxed cellularstructure appears in upper melt region nearly surface.The substructure of cellular grains anddendrites was observed to consist of martensite and retained austenile,while the carbides asM_6C_■ Cr_7C_3 and MC distributed at their boundaries.It is believed that the highermicrohardness up to HV_(0.1)=865-960 of the laser fused structure of the alloy is due to the oc-currence of martensite.
基金the National Natural Science Foundation of China(No. 50575173).
文摘Under spinning conditions, lubricant on islandic spot patterned M2 steel disc experiences centrifugal and tangential force components. Depending upon the relative position of the spots and the flow of lubricant, accumulation of lubricant in front of patterned islandic spots creates thrusting to mating part and subsequently reduces contact between the mating couple. Whilst wear debris is likely to be spun off the plateau of the spots to their neighbouring valleys so as to reduce wear. Hence, it gives favorable tribological characteristics. Aiming at verifying such mechanisms, studies were performed on M2 steel disc specimens slid with ASSAB 17 tool steel pin. The M2 steel disc specimens were respectively （i） machined with non-patterned （NP）, （ii） etched to produce in-lined （INE） islandic patterns, and （iii） etched to produce staggered （STE） islandic spot patterns. Results indicated that the INE patterned discs gave most favorable wear characteristics, the NP of the worse characteristics whilst the STE ranged in the middle. However, the actual contact mechanism leads to the descending sequence of favorable friction behaviors nominally as： NP, INE and STE.
文摘The cyclic plastic straining electrode technique has been used to investigate the transient electrochemical behaviour of Fe-26Cr1Mo stainless steel in 1M H2SO4 solution at a passive potential.The influence of plastic strain amplitude and plastic strain rate on the dissolution current response was analysed. The experimental results showed that the transient current was dependent on the competitive process of the surface film rupture and repassivation of the new surface. The high plastic strain amplitude and the high plastic strain rate caused a change of electrochemical activity of specimen surface. In the condition of low strain amplitude and strain rate, the characteristics of current response was mainly relative tp the process of new surface repassivation.The competition kinetics has been analysed through the comparison of plastic strain rate and repassivating rate
文摘在实验室条件下采用立式连铸的方法连铸φ100 mm M2钢,在扫描电镜下观察分析其碳化物的分布、形貌、尺寸和类型,研究了析出碳化物的演变规律,并对其在液相区、固-液两相区和固相区的析出规律进行了热力学计算。结果表明:φ100 mm M2钢连铸坯碳化物呈网状分布,网状碳化物的厚度从铸坯边部的1.5μm增大到中心的30μm,增大约20倍。碳化物形貌包括:块状、片层状和棒状,其中块状碳化物为VC,而片层状和棒状碳化物为M_2C。在液相和固-液两相区δ铁素体析出过程中,各种碳化物均不具备析出的热力学条件;在固-液两相区中γ奥氏体转变过程中,W_2C在1504 K具有析出的热力学条件;当温度降到固相线以下时,碳化物的析出顺序为VC>Mo_2C>W_2C,其析出温度分别为1475 K、549 K和333 K。
