Cr_3C_2含量和快淬速度对SmCo_(7-x)(Cr_3C_2)_x合金非晶化行为的影响(英文)

通过X射线衍射法(XRD)、差示扫描量热法(DSC)和磁性测量等方法系统研究Cr3C2含量和快淬速度对SmCo7-x(Cr3C2)x(x=0.10-0.25)非晶化行为的影响。结果表明,在低的快淬速度下(20m/s)下,合金主要由SmCo7主相和少量Sm2Co17R相构成,且SmCo7相的晶粒尺寸随着Cr3C2含量x的增加而减小。随着快淬速度的增加,合金的XRD衍射峰强度变弱、衍射峰宽化,表明SmCo7主相的晶粒尺寸随着快淬速度的增加而减小。当快淬速度增加至40m/s时,SmCo7-x(Cr3C2)x(0.15≤x≤0.25)合金均形成了非晶态结构,合金的磁滞回线表现为软磁性的窄回线,矫顽力为0.004~0.007T。采用DSC对合金的晶化行为分析表明,在650°C时SmCo7相首先从非晶基体中析出,在770°C时Sm2Co17相析出。     

Co元素及凝固速度对La-Fe-Si系NaZn_(13)型相及磁性能的影响

采用熔体快淬法制备不同快淬速度的La_(0.8)Ce_(0.2)(Fe_(11.5-x)Co_x)Si_(1.5)(x=0.0,0.3,0.5,0.7)合金条带,经过1273 K/20 min热处理,通过X射线衍射和磁性测量研究Co元素及凝固速度对La-Ce-Fe-Co-Si合金的相形成和磁性能的影响。结果表明:Co元素添加和快淬速度提高均有利于Na Zn13型相的形成;Co元素添加提高合金居里温度,减小磁滞,但是磁热性能有所降低;快淬速度提高导致合金的磁滞增大,但对磁热性能影响较小。     

Sm5Fe80Cu1Zr3.5Si5B3C2.5非晶合金晶化动力学的研究

利用X射线衍射、透射电镜、振动样品磁强计和差热分析研究了非晶Sm5Fe80Cu1Zr3.5Si5B3C2.5合金中α-Fe/Sm2(Fe,Si)17Cx复合纳米相结构的形成过程、磁性及其晶化动力学.XRD结果表明,随着退火温度的升高,Sm5Fe80Cu1Zr3.5Si5B3C2.5非晶合金先后析出软磁相α-Fe和硬磁相Sm2(Fe,Si)17Cx;当经高温750℃晶化退火后,经Scherrer计算得到合金中α-Fe相和Sm2(Fe,Si)17Cx的晶粒尺寸分别为65.5和22.1nm,其矫顽力增加到58.11kA/m,剩磁为0.967T.晶化动力学分析发现,这种具有较低初始晶化激活能和阶段生长激活能的晶化行为是导致α-Fe相晶粒生长过于粗大和合金中α-Fe和Sm2(Fe,Si)17Cx复合纳米磁体磁耦合性能较差的根本原因.     

非晶Al85Y4Nd4Co7合金及其晶化行为

采用单辊旋淬快速凝固方法制备出Al85Y4Nd4Co7的合金薄带,对快速凝固合金进行差示扫描量热(DSC)、X射线衍射(XRD)和透射电镜(TEM)分析.结果表明,在铸态时,得到完全非晶组织;经280℃×1.5 h退火,快凝合金中有α-Al析出;经350℃×1.5 h退火处理后,有Al3Y和Al9Co2相析出;450℃×1.5 h退火后,有新相A13Nd和未知相析出,且已有晶粒都明显长大.     

快淬速度对Nd2Fe14B/α-Fe纳米复合永磁材料结构和磁性能的影响

利用熔体快淬法制备了(Nd0.9Dy0.1)9(Fe0.9Co0.1)85.5B5.5快淬薄带,研究了快淬速度对晶化过程、晶化后薄带的结构及磁性能的影响.研究发现,快淬速度不同,薄带的非晶程度不同,晶化过程存在很大差异;在快淬速度为12m/s时,快淬薄带中已存在一定的晶态相,晶化后的晶粒细小均匀,磁性能较高;而当快淬速度达到18m/s和25m/s时,合金晶化后的晶粒粗大且不均匀,磁性能较低.     

Co含量对熔体快淬Fe_(55-x)Co_xPt_(15)B_(30)合金的组织结构与磁性能的影响

研究了Co含量对熔体快淬Fe_(55-x)Co_xPt_(15)B_(30)(x=0~45,原子分数,%)合金热处理前后的组织结构和磁性能的影响。结果表明,添加Co可提高Fe_(55-x)Co_xPt_(15)B_(30)合金的非晶形成能力,使x=15~45的快淬合金形成非晶态。经适当热处理后,合金中形成了由有序面心四方结构的永磁(Fe,Co)-Pt(L1_0)相和软磁(Fe,Co)2B相及(Fe,Co)B相组成的纳米复相组织,显示出永磁性;添加Co的合金组织得到明显细化,x=15~45合金平均晶粒尺寸均约为18 nm;其中x=15合金具有最佳的永磁性能,磁能积达到94.4 k J/m3。合金的矫顽力随Co含量的增加而增大,在x=30时达到最大值413.7 k A/m后,随Co含量的进一步增加而减小;这是由于不同Co含量使L1_0相的c/a值发生变化而导致其磁晶各向异性变化的结果。     

退火温度对Fe-Co-(Nb,V)-B-Cu非晶合金组织及软磁性能的影响

采用单辊旋淬法制备出Fe69Co8Nb7-xVxB15Cu1(x=0,2,5,7)系列非晶合金,将非晶合金在不同温度进行退火,通过X射线衍射仪、透射电镜和B-H磁滞回线仪对退火后合金的微观组织和软磁性能进行分析。结果表明:退火温度对合金的微观组织和软磁性能影响显著,当TaTg时,由于结构弛豫,内应力的释放,非晶合金的矫顽力(Hc)降低;当Tx1TaTx2时,由于bcc结构α-Fe(Co)纳米晶相的析出,合金的饱和磁感应强度(Bs)明显增大;当TaTx2时,由于α-Fe(Co)晶粒粗化和非磁性相的析出,合金的软磁性能急剧恶化。其中Fe69Co8Nb5V2B15Cu1非晶合金在580℃退火1 h,表现出极为优异的软磁性能,其Bs=1.15 T,Hc=0.9928 A/m,μi=48460,而Fe69Co8V7B15Cu1非晶合金在650℃退火1 h,则发生软磁到硬磁性能的转变。     

(Fe1-xCox)78.4Nb2.6Si9B9Cu1纳米晶软磁合金的结构与高频磁性

研究了非晶(Fe1-xCox)78.4Nb2.6Si9B9Cu1(x=0.35,0.5,0.65)合金490℃等温退火0.5 h后的结构与高频磁性.XRD分析表明,退火后非晶合金实现纳米晶化,析出晶粒尺寸约15 nm的α-FeCo(Si)软磁晶体相;随Co含量增加,晶格常数变小.利用Pseudo-Voigt2函数模拟XRD衍射峰并计算了晶体相体积分数,由晶体相体积分数及晶格常数估算了剩余非晶相的成分.用阻抗分析仪测量了合金在10 kHz-10 MHz范围的磁谱曲线.结果表明,随Co含量增加,合金初始磁导率降低,而共振频率明显提高,用畴壁运动方程及畴壁钉扎理论解释了Co含量变化对纳米晶合金高频磁性的影响规律.     

Fe_(52-x)Co_(14)Nb_4Mo_3Ni_5B_(22)Cr_x多组元块体非晶合金的热学和软磁性能

采用铜模铸造法制备Fe_(52-x)Co_(14)Nb_4Mo_3Ni_5B_(22)Cr_x(x=0, 2, 3, 4; at.%)多组元块体非晶合金。采用X射线衍射仪(XRD)、差示扫描量热分析仪(DSC)和振动样品磁强计(VSM)等手段探究了Cr含量对合金非晶形成能力及软磁性能的影响。DSC曲线表明,合金经历2次晶化过程,Cr含量增加使得合金成分接近深共晶点。随着Cr含量的增加,合金的过冷液相区ΔTx由36 K增加到51 K,晶化起始温度Tx1由842 K增加至872 K。VSM结果表明,Fe_(52-x)Co_(14)Nb_4Mo_3Ni_5B_(22)Cr_x非晶合金其饱和磁感应强度Ms随着Cr含量的增加而减小。制备得到的多组元块体非晶合金具有高非晶形成能力和优异软磁性能,适合于作为一款优异的磁性元器件材料使用。     

快淬纳米晶/非晶Mg2-xLaxNi (x=0~0.6)合金的电化学贮氢性能

用铸造及快淬工艺制备Mg2Ni型Mg2-xLaxNi(x=0,0.2,0.4,0.6)贮氢合金。用XRD、SEM、HRTEM分析铸态及快淬态合金的微观结构。结果发现,在快淬无La合金中没有出现非晶相,但快淬含La合金显示了以非晶相为主的结构。用DSC研究快淬合金的热稳定性,表明La的含量及快淬对非晶相的晶化温度影响很小。电化学测试结果表明,铸态合金的放电容量随La含量的增加而增加,快淬态合金的放电容量随La含量的变化有极大值。La替代Mg显著地提高了铸态及快淬态合金的循环稳定性。     

超细Cr_3C_2粉末的制备

将CrO3溶解于有机溶液中,通过喷雾干燥制得非晶态含铬的粉末前驱体,将前驱体粉末真空还原/碳化后得到超细Cr3C2粉末。采用X射线衍射仪﹑扫描电镜对工艺过程进行分析,分析结果表明:前驱体为10μm～20μm非晶态球形粉末,在真空中当温度升高到400℃时,前驱体粉末开始分解,生成微晶Cr2O3。当温度升高到550℃时,微晶Cr2O3迅速长大,前驱体粉末全部转变为Cr2O3与游离C原子级别混合均匀的复合粉末;温度升高到1150℃时得到碳化完全的Cr3C2粉末,粉末的一次颗粒粒度为0.5μm左右。     

Thermal stability of nanostructured Cr3C2-NiCr coatings

The thermal stability behavior of nanostructured Cr₃C₂-NiCr coatings was investigated. The nanostructured Cr₃C₂-NiCr coatings, synthesized using mechanical milling and high-velocity oxygen fuel (HVOF) thermal spraying, were thermally exposed in air at 473, 673, 873, and 1073 K for 8 h. The results show that microhardness of the conventional coating increased slightly with increasing temperature, while that of the nanostructured coating drastically increased from 1020 to 1240 HV₃₀₀ for the same temperature increases. Heat treatment led to increases in scratch resistance and decreases in the coefficient of friction for the nanostructured Cr₃C₂-NiCr coatings. A high density of Cr₂O₃ oxide particles with average size of 8.3 nm was found in the nanostructured coatings exposed to high temperatures, which is thought to be responsible for the observed increase in microhardness and scratch resistance and the decrease in the coefficient of friction of the nanostructured coatings.     

Erosion Performance of HVOF-Sprayed Cr3C2-NiCr Coatings

Cr₃C₂-NiCr coatings were deposited by high-velocity oxygen fuel (HVOF) spraying process under spray conditions of different flows of oxygen and propane gases, and spray distances. The orthogonal regression experimental design method was used for systematic investigation of the influence of spray parameters on the erosion performance of Cr₃C₂-NiCr coatings. Erosion tests were performed at different jet angles of abrasive particles. The erosion mechanism of Cr₃C₂-NiCr coatings was examined through the surface morphology and cross-sectional microstructure of the eroded coatings. The correlations of the carbide particle size and carbide content with the erosion rate were examined. It was found that the erosion occurred dominantly by spalling of splats from the lamellar interfaces. The spalling resulted from the propagation of cracks parallel to the interfaces between the lamellae exposed to the surface and underlying coating. The carbide particle size and content in the coating influenced significantly the erosion performance of Cr₃C₂-NiCr coatings.     

Mechanical and tribological properties of plasma-sprayed Cr3C2-NiCr, WC-Co, and Cr2O3 coatings

Mechanical properties such as Young’s moduli and fracture toughness of plasma-sprayed Cr₃C₂-NiCr, WC-Co and Cr₂O₃ coatings were measured. The tribological properties of the three kinds of coatings were investigated with a block-on-ring self-mated arrangement under water-lubricated sliding. Furthermore, the influences of the mechanical properties on the tribological properties of the coatings were also examined. It was found that the Young’s moduli, bend strengths and fracture toughness of the coatings were lower than the corresponding bulk materials, which may be attributed to the existence of pores and microcracks in the coatings. Among the three kinds of coatings, the magnitude of wear coefficients, in decreasing order, is Cr₃C₂-NiCr, WC-Co and Cr₂O₃, and the wear coefficient of Cr₂O₃ coating was less than 1 × 10⁻⁶mm³N⁻¹m⁻¹. The wear mechanisms of the coatings were explained in terms of microcracking and fracturing, and water deteriorated wear performance of the coatings. The higher the fracture toughness and the lower the porosity and length of microcracking of the coating, the more the wear-resistance of the coating.     

HVOF喷涂Cr3C2-NiCr涂层的磨粒磨损性能

探讨了氧气流量、燃气流量和喷涂距离三个喷涂工艺参数对ＨＶＯＦ喷涂Ｃｒ３Ｃ２－ＮｉＣｒ涂层硬度和磨粒磨损性能的影响。结果表明,燃气流量、氧气流量和喷涂距离对涂层的显微硬度和磨粒磨损性能的规律有所不同。在较高的燃气流量、适中的氧气流量和喷涂距离条件下,涂层具有较高的显微硬度;而氧气流量和燃气流量对涂层的磨粒磨损性能影响较大,适中的燃气流量条件下,涂层的磨粒磨损失重量较低,高的氧气流量条件下,磨损失重量     

Cr3C2/Ni3Al复合材料的微观组织和室温耐磨性

采用药芯焊丝法制得Ni-Al-Cr3C2复合焊丝,将该焊丝堆焊于工件表面,在堆焊过程中,利用氩弧物理热和Ni-Al反应热,Ni与Al化合反应生成Ni3Al金属间化合物,Cr3C2则发生分解,除少部分[C]与[Cr]固溶于Ni3Al基体中外,大部分反应重新析出细小的Cr3C2相,均匀地分布于Ni3Al基体中.室温磨粒磨损和微动磨损实验结果表明,Cr3C2/Ni3Al复合材料的耐磨性为Stellite12合金的2倍左右,较高的硬度、高的碳化物体积分数以及碳化物与Ni3Al基体间良好的界面结合力是Cr3C2/Ni3Al复合材料耐磨性优良的主要原因.     

超音速火焰喷涂Cr3C2-NiCr涂层磨粒磨损行为

采用橡胶轮磨损实验机，对不同工艺条件下三种类型粉末制备的HOVF Cr3C2-25％NiCr涂层进行了磨粒磨损实验，发现该涂层的磨损失重量与磨程基本呈现线性关系，磨损率远低于低碳钢。氧气流量，燃气流量适中的条件下制备的涂层磨损率较低，用团聚致密化工艺制备的粉末沉积的涂层耐磨粒磨损性能较好，涂层的磨损机制主要为先期的粘结相优先切削和随后的碳化物剥落，其中碳化物的剥落对磨损过程起制约作用。     

Cr_3C_2粉体的高能球磨细化

采用高能球磨工艺对Cr3C2粉末进行研磨。研究了粉体粒度随球磨时间的变化。结果表明:随着球磨时间的增加,粉体粒度不断细化,最后BET粒度趋于稳定在50nm左右。Cr3C2粉末高能球磨细化机理是:机械力通过破碎一次颗粒间的烧结颈,并不断细化粉末,Cr3C2粉末的最终粒度取决于一次颗粒的晶粒尺寸;长时间球磨不能进一步细化粉末反而容易形成新的团聚体。     

Wear resistance of a Cr3C2-NiCr detonation spray coating

Coatings can be applied to surfaces to improve the surface characteristics over those of the bulk properties and are widely used in tribological applications either to reduce wear and/or to modify friction during contact. One of the foremost coating methods for combating wear is thermal spraying. To prolong the life of steel slab continuous casting rolls, Cr₃C₂-NiCr detonation spray coating was processed on the roll surface in a steelmaking plant in China. This article studies the mechanical properties and wear resistance of this coating. The abrasive and dry frictional wear testing were performed using a pin-on-disk tester. Experimental results show that the wear resistance of the coated samples, i.e., coating reduces the risk of seizure compared to uncoated samples, is much better than those of the uncoated steel at room and elevated temperatures with any load and sliding velocity. The coating wear mechanisms under different test conditions are discussed.