共查询到19条相似文献,搜索用时 328 毫秒
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研究了微量硼对M2高速钢的凝固组织以及热处理过程中共晶碳化物团球化的影响及其机理。发现,硼促进层片状M2C碳化物的形成;促进共晶碳化物的偏析,使碳化物量增加,层片变粗;促进共晶碳化物在高温加热时的断网和团球化,在高速钢中硼主要偏聚在晶界共晶碳化物上。 相似文献
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为提高中铬铸铁共晶碳化物中M7C3比例,研究了中铬硅铸铁(290Cr8Si2).建立了铸态中铬硅铸铁基体的价电子结构,运用固体与分子经验电子理论(EET)分析了中铬硅铸铁中Si的作用.分析和实验结果表明,中铬硅铸铁基体含C、Cr、Si的γ-Fe晶胞中,C原子与Si原子的结合力强于C原子与Cr原子的结合力,较高的含Si量降低了铸铁基体的含Cr量,提高了共晶碳化物的含Cr量,进而提高了共晶碳化物中M7C3的比例.耐磨损中铬硅铸铁(290Cr8Si2)共晶碳化物(M7C3 M3C)中M7C3占94.2%(体积分数),明显高于中铬铸铁(290Cr8Si1)共晶碳化物中的M7C3的71.7%(体积分数). 相似文献
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采用原位合成法制备ZrB_2/A356.2复合材料,研究了引入ZrB_2对A356.2铸态微观组织的影响以及不同Er含量对复合材料铸态微观组织及力学性能的影响。结果表明,引入ZrB_2后α-Al晶粒和粗大共晶Si发生略微细化,添加Er后α-Al晶粒细化明显,并且Er对共晶Si有很好的变质效果,α-Al由粗大树枝晶变为蔷薇状、球状,共晶Si从粗大的针片状变为细小的短棒状、球状,有效提高了复合材料的力学性能。当Er添加量为0.10%(质量分数)时,其细化变质效果最为明显,复合材料力学性能提高最为显著。 相似文献
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研究电脉冲处理对铸态W6Mo5Cr4V2高速钢组织的影响及其机理,利用光学显微镜、XRD和EDS观察成分和微观组织的变化。结果表明:铸态高速钢的微观组织主要由MC,M_2C和M_7C_3碳化物和马氏体、奥氏体、珠光体混合组成,碳化物在晶界处呈连续的网状分布,存在部分鱼骨状共晶碳化物;经过脉冲电流处理后,碳化物的物相种类未发生变化,但形态上由网状趋向于断裂,有明显的孤立和球化趋势,鱼骨状共晶碳化物消失,同时,碳化物含量减少,而基体中合金元素含量增加,基体的硬度提高。焦耳热和电磁力偶合物理效应是造成这些现象的主要机理。 相似文献
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研究了传统电渣重熔工艺(ESR)和电渣重熔连续定向凝固技术(ESR-CDS)所得到的M2高速钢铸态显微组织。结果表明:采用ESR工艺得到铸态组织边部为树枝晶且部分出现了三次枝晶,心部为粗大的等轴晶,晶粒之间有网状碳化物,铸锭的偏析较为严重,经深腐蚀凝固组织基体与碳化物过渡区较为疏松、粗糙,部分基体内部出现了细小的裂纹。而采用ESR-CDS工艺得到铸态组织边部和心部都以较为细小的树枝晶为主,组织中存在比较多的"不连续的复合规则型"的碳化物,组织较为均匀,经深腐蚀,碳化物与基体过渡区圆滑。 相似文献
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本工作利用自熔铸渗技术在ZG45钢表面复合不同硼含量的高铬铸铁铸渗层,研究了硼对高铬铸铁铸渗层组织和性能的影响.利用相图计算软件Thermo-Calc计算分析了不同硼含量下铸渗层的凝固过程,并采用SEM-EDS、XRD和显微硬度仪对不同成分铸渗层的微观组织和硬度进行分析.结果表明:铸渗层与ZG45钢基体达到冶金结合,在结合界面处未观察到微孔洞、微裂纹等缺陷,获得了厚度为10~12 mm的铸渗层.不含硼的铸渗层组织由α-Fe和α-Fe+M7 C3共晶组织组成.加入微量的硼元素后,铸渗层组织主要由α-Fe与α-Fe+M7 C3+M2 B共晶组织组成,与相图计算结果基本吻合.随着硼含量的增加,共晶组织逐渐细化,M7 C3碳化物含量减少,M2 B型硼化物增多,铸渗层硬度逐渐增加.当硼含量为0.72%(质量分数)时,铸渗层硬度最高达到1190HV.对铸态试样进行淬火+低温回火热处理后,铸渗层共晶硼化物与碳化物发生聚集长大,同时在铸渗层基体中伴有二次相的析出,试样铸渗层的洛氏硬度均有提升.热处理试样冲击磨损实验表明,铸渗层磨损表面主要以切削犁沟、疲劳剥层和剥落坑为主,并有少量微小的凿坑.硼含量为0.72%(质量分数)时,试样的抗冲击磨损性能最佳. 相似文献
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研究了CoCrMo合金普通壳型铸造工艺下过热度和高温固溶热处理对显微组织的影响。结果表明:CoCrMo合金在铸态下碳化物主要以大块状共晶状M23C6碳化物存在;随着过热度的增加,碳化物共晶团的尺寸增大,导致室温拉伸性能降低。CoCrMo合金经过高温固溶热处理后,大部分大块状共晶碳化物发生溶解和分解,以细小的颗粒状M23C6碳化物析出并均匀分布于基体,抗拉强度、屈服强度和伸长率得到很大的提高。均匀细小分布的碳化物有利于提高CoCrMo合金的室温拉伸性能。 相似文献
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H. B. Wang L. G. Hou J. X. Zhang L. Lu H. Cui J. F. Huang J. S. Zhang 《Materialwissenschaft und Werkstofftechnik》2014,45(8):689-698
The billets of M3 high speed steel (HSS) with or without niobium addition were prepared via spray forming and forging, and the corresponding microstructures, properties were characterized and analysed. Finer and uniformly‐distributed grains without macrosegregation appear in the as‐deposited high speed steel that are different to the as‐cast high speed steel, and the primary austenite grain size can be decreased with 2% niobium addition. Niobium appears in primary MC‐type carbides to form Nb6C5 in MN2 high speed steel, whereas it contributes less to the creation of eutectic M6C‐type carbides. With same treatments to forged MN2 high speed steel and M3 high speed steel, it is found that the peak hardness of these two steels are almost the same, but the temper‐softening resistance of the former is better. With higher high‐temperature hardness of the forged MN2 high speed steel, its temper softening above 600 °C tends to slow down, which is related to the precipitation of the secondary carbides after tempering. A satisfactory solid solubility of Vanadium and Molybdenum can be obtained by Nb substitution, precipitation strengthening induced by larger numbers of nano‐scaled MC and M2C secondary carbides accounts for the primary role of determining higher hardness of MN2 high speed steel. The results of the wear tests show that the abrasive and adhesive wear resistance of MN2 high speed steel can be improved by the grain refinement, existence of harder niobium‐containing MC carbides, as well as solute strengthening by more solute atoms. The oxidational wear behavior of MN2 high speed steel can be markedly influenced by the presence of the high hardness and stabilization of primary niobium‐containing MC‐type carbides embedded in the matrix tested at 500 °C or increased loads. The primary MC carbides with much finer sizes and uniform distribution induced by the combined effects of niobium addition and atomization/deposition would be greatly responsible for the good friction performance of the forged MN2 high speed steel. 相似文献
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《Materials Science & Technology》2013,29(5):449-454
AbstractThe effect of vanadium (0–4%) on the morphology and amount of eutectic and eutectoid carbides in high speed steels has been investigated using scanning electron microscopy and image analysis. It was found that vanadium promotes the formation of MC carbide and M2C carbide, but inhibits the formation of M6C carbide. In the vanadium free steels, the eutectic carbide consists solely of skeletal M6C. For each steel composition, there is a critical vanadium content at which the skeletal eutectic changes to lamellar eutectic and the critical value decreases as the molybdenum content of steel increases. The effect of vanadium on the total amount of eutectic carbide differs in tungsten alloyed and molybdenum alloyed high speed steels. The δ eutectoid has a rodlike morphology in tungsten high speed steels; δ eutectoid is not present in Mo–W or molybdenum high speed steels. Increasing the vanadium content leads to an increase in the size of eutectic and eutectoid carbides.MST/1264 相似文献
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M2 cast high speed steel was inoculated by addition of rare earth(RE)‐Al‐N, network eutectic carbides were eliminated, matrix structures were refined and the segregation of tungsten and molybdenum elements were relieved. In the condition that the hardness did not decrease, impact toughness obviously increased. Quenching at 1180 °C and three‐times tempering at 560 °C, the hardness of M2 cast high speed steel kept 65~66HRC, impact toughness reached 21.3J/cm2. Modified M2 cast high speed steel had excellent thermal fatigue resistance and high temperature wear resistance. Roll made in modified M2 cast high speed steel had excellent service effect using in slit rolling mill stand of hot rolling bar mill. 相似文献
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为研究硅对烧结高速钢力学性能的影响,采用真空热处理炉在1230℃对含0.4%碳粉及硅添加量在0~3.0%的M3∶2高速钢进行烧结,在500~600℃对烧结后的试样进行二次回火.采用X射线衍射仪,扫描电镜及能谱分析等手段研究了不同硅添加量对回火态高速钢的物相特征及力学性能的影响规律.物相分析结果表明,添加硅后,硅主要分布在回火马氏体及M6C碳化物中,而在MC碳化物中含量较低.回火马氏体组织中硅的含量随硅添加量的增加而增加,同时,硅的添加还显著影响回火马氏体组织中铁素体相的晶格常数,在硅添加量为0.7%时,铁素体相达到最大的晶格常数.力学性能测试结果表明,适量硅的添加可提高二次硬化效果,添加0.7%硅的高速钢在550℃二次回火后获得了最佳的硬度和弯曲强度. 相似文献
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The densification and microstructural evolution during co-sintering of M2 tool steel/316L stainless steel composite layers
with and without boron addition was studied. A pressureless sintering method in conjunction with a powder layering technique
was used to fabricate the stepwise graded composite layers. Isothermal and non-isothermal sintering response of the individual
and composite layers was examined and the microstructural features of the bonding zone were studied. Shear strength and microhardness
of the bonding zone were also measured. It was shown that an enhanced densification is obtained in the composite layers due
to (i) sintering shrinkage incompatibility between two steels, (ii) interlayer diffusion of the alloying elements and formation
of a dual δ-ferrite/austenite phase at high temperature, and (iii) formation of a low temperature eutectic Fe (C)-B phase
at the interface in the samples containing boron. The morphology of carbides in M2/316L is significantly changed as the sintering
temperature increases, i.e., they appeared as fine intergranular carbides at low temperatures (1,240 °C), thick film at 1,260 °C
and herringbone shape eutectic at 1,290 °C. Elongated grains with an intergranular boride phase were seen in the bonding zone
of M2/316L + B layers. The shear strength of the interface of the composite layers was found to be superior to that of the
individual layers. 相似文献
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Thermal analyses and microstructural evaluation were carried out for the conventional AISI M2 and M10 high speed steels as well as for alloys with varying Nb and/or Ti contents to assess their liquidus, solidus and other high temperature reactions. It has been found that the slope change of cooling curves marks the formation of MC type carbides, while the break is due to the crystallization of delta ferrite and much larger volume fraction of different type of carbides including M6C mostly by eutectic reactions. Results show that the formation of dendrites is the most basic characteristic of the solidification process for the AISI M2 and M10 alloys but for the steels containing niobium and/or titanium carbides, these primary carbides insert an inoculating effect and modify the coarse dendritic structure. 相似文献
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本文利用扫描电镜、能谱分析对三种轧辊用高速钢的组织中碳化物进行了研究,并分析了VC形态与高速钢化学成分之间的关系。结果表明:轧辊用高速钢组织包括马氏体基体,残余奥氏体和各种类型碳化物,如粒状或小块状的MC型碳化物,网状的M7G型碳化物,鱼骨状的M6C型碳化物以及其他复合型碳化物,各种碳化物含有的合金元素以及显微硬度不同;在研究范围内(Weq≤10),晶粒尺寸是随钨当量的升高而变小;根据V含量不同,VC会出现不同形貌进而影响高速钢性能。 相似文献