激光熔覆铁基复合涂层组织与性能影响

目的 在45#钢基体表面制备耐磨性优于基材的梯度涂层。方法 采用激光熔覆技术在基材上制备连接层后,分别用未添加WC颗粒、添加3%和5%WC颗粒的铁基合金粉末制备耐磨涂层。通过金相显微镜（OM）、X射线衍射仪（XRD）、扫描电子显微镜（SEM）,研究了涂层的微观结构。通过维氏显微硬度计和M-2000磨损试验机,研究了涂层的力学性能。结果 获得的涂层致密,没有裂纹和气孔等缺陷,涂层内部WC清晰可见。连接层与基材具有良好的冶金结合,涂层组织主要有等轴组织、柱状组织和共晶组织。耐磨层物相组成为奥氏体（γ-Fe）、γ(Fe,Ni)固溶体和Fe-Ni-Cr固溶体。涂层表面的显微硬度最高为559HV1,比基材硬度（182HV1）提升了3倍多。随着WC含量的增加,涂层的磨损量显著下降。结论 基材与连接层有沿基体表面生长的平面晶,涂层内部为柱状晶、树枝晶和共晶等组织,涂层顶部多为细小的等轴晶。加入WC,涂层的显微硬度提高不明显,但WC周围的组织细化,显微硬度提高。无WC的涂层磨损机理主要为粘着磨损;3%WC的涂层磨损较轻,磨损仍以粘着磨损为主;5%WC的耐磨层磨损最轻,磨损机理为磨粒磨损,WC的加入明显提高了涂层的耐磨性。     

保护气体对碳化钨药芯焊丝堆焊层组织及性能的影响

采用自制药芯焊丝,利用3种保护气体(纯氢气,80%Ar+20%CO2和纯CO2气体)制备碳化钨/铁基堆焊层,对不同保护气体下WC颗粒溶解扩散、堆焊层组织、硬度及耐磨性进行研究. 结果表明,采用纯氩气保护堆焊时,WC颗粒的溶解扩散层宽度约为3 μm,WC颗粒边缘以须状共晶组织为主,焊层显微硬度为790 HV±20 HV,磨损量为11.4 mg;保护气体为纯CO2时,扩散层宽约为5 μm,共晶组织形态为菊花状、鱼骨状或类团絮状,显微硬度为590 HV±15 HV,堆焊层表面磨损程度小,磨损量为4.2 mg,较纯氩气保护降低了63%倍,耐磨性相对较好.     

激光熔凝对高速火焰喷涂硬质合金层耐磨性的影响

利用高速火焰喷涂在45钢表面制备了Ni60AA和DZ-WC-12Co硬质合金层,再采用5 k W连续CO2激光器进行激光熔凝。通过GX51金相显微镜观察显微组织,HXS-1000TAY维氏硬度计测量硬度分布,MM-W1B立式万能磨损试验机进行磨损试验。结果表明,激光熔凝显著地消除了硬质合金层中未熔硬质合金颗粒、孔洞及裂纹等缺陷,组织更加细小、均匀;激光熔凝后,硬质合金层的硬度提高,平均显微硬度高达647 HV0.3。在试验条件下,激光熔凝后的硬质合金层的摩擦因数从原来的0.1373降至0.0948,激光熔凝可明显改善涂层的耐磨性能。     

TiC含量对激光合金化层组织和耐磨性的影响

以亚微米级TiC和WC作为陶瓷硬质相,自制的合金粉末作为粘结相,采用激光表面合金化技术在球墨铸铁表面制备出高硬度、耐磨的合金化层.利用扫描电子显微镜(SEM)、EDAX能谱仪(EDS)、X射线衍射仪(XRD)等分析测试手段对不同TiC含量下的合金化层的显微组织和物相构成进行了分析,并对合金化层进行了硬度和摩擦磨损性能测试.结果表明,随着涂料中TiC含量的增加,合金化层中碳化物硬质强化相逐渐增多,合金化层的硬度和耐磨性也逐渐提高.当TiC含量为40%时,合金化层的性能较好,平均显微硬度可达1097 HV0.2,其磨损量仅为基材球墨铸铁的1/9.     

电渣熔铸钢结硬质合金经激光熔化处理后的组织和性能

借助光学显微镜、扫描电镜及XRD衍射仪对重熔层的显微组织结构和相结构进行分析，用显微硬度计和MM-200型磨损试验机对激光处理表面的硬度和耐磨性进行了测试。试验结果表明，电渣熔铸钢结硬质合金表面经过激光重熔处理后的组织比未经激光处理的明显细化，大颗粒WC部分溶解，小颗粒碳化物完全溶解；随着激光功率的加大，重熔层的熔深增大，枝晶尺寸随之增大，表面硬度和耐磨性也相应提高。     

9CrSi钢表面激光合金化的组织与性能

以亚微米级WC/Co金属陶瓷复合材料为涂层材料,采用激光合金化技术在9CrSi表面制备出硬度高、耐磨的合金化层.利用扫描电子显微镜(SEM),X射线衍射仪(XRD)等分析测试手段对激光合金化层的显微组织和物相构成进行了分析,并对合金化层进行了硬度和摩擦性能测试.结果表明,激光合金化层与基材形成了良好的冶金结合.激光合金化层可分为合金化区,热影响区和基体区三部分.其中合金化区组织为基体马氏体上分布着网状枝晶碳化物,网状枝晶间弥散分布着碳化物小颗粒,热影响区组织由马氏体及残留奥氏体组成,基体区组织无明显变化.合金化层的显微硬度达到900 HV0.2,干摩擦条件下材料磨损量是基材9CrSi的1/9,合金化涂层的耐磨性得到显著的提高.     

镍基碳化钨颗粒增强复合熔覆层的组织结构与摩擦学性能

借助激光熔覆方法在H13钢基材上制备不同WC含量的Ni基WC复合熔覆层,采用扫描电子显微镜(SEM)、微区X射线能谱(EDS)和X射线衍射仪(XRD)分析了熔覆层表面的物相、熔覆层与基材的结合情况、熔覆层内部增强相的形貌、成分与分布;在室温下测试显微硬度、摩擦因数和磨损率。结果表明:基体和熔覆层之间为冶金结合,熔覆层物相为γ-Ni相、WC、Cr23C6、W2C相,这些碳化物呈现近圆形;激光熔覆层中Ni基体的显微硬度为550-700 HV0.1,硬质相颗粒的显微硬度为2700~3500 HV0.1,是基材显微硬度的5~7倍;Ni基+30%WC熔覆层的摩擦因数为0.7,磨损率为1.92×10~(-8)mm~3/(N·m)。随着WC含量增多45%,耐磨性进一步提高、摩擦因数约为0.4,磨损率为8.32×10~(-9)mm~3/(N·m),WC含量达到60%,摩擦因数为0.5、磨损率与45%WC熔覆层磨损率接近;综合比较,45%WC激光溶层耐磨减摩效果最佳。     

双层WC颗粒增强铁基体复合熔覆层的组织和性能研究

采用氩弧熔覆(GTAW)技术在45号钢表面制备了双层WC颗粒增强铁基体复合涂层,通过SEM,XRD和EDS分析了熔覆层的显微组织和相组成,并测试了熔覆层的显微硬度.结果表明:双层复合熔覆层内未见明显裂纹、夹杂等缺陷,与基体呈冶金结合;熔覆层的显微组织由未熔WC颗粒、灰色等轴状初晶和鱼骨状共晶碳化物组成;复合熔覆层的显微...     

激光熔覆TiC-WC增强NiCrMn合金涂层组织与性能

利用激光熔覆技术在0Cr18Ni9奥氏体不锈钢表面制备了NiCrMn-TiC/WC-La_2O_3硬质合金耐磨涂层。采用X衍射仪、扫描电镜、能谱仪分析了熔覆层的物相组成及显微组织。测试了涂层的显微硬度,并在室温环境下对涂层进行干滑动摩擦磨损试验。结果表明:涂层主要由γ-(Ni,Fe)共晶化合物、未溶解的TiC和WC、原位生成的M_7C_3、TiC和(Ti,W)C、WC碳化物硬质相以及少量La_2O_3和Cr_3C_2组成。激光熔覆层的显微硬度大幅提高,显微硬度平均值为1172.74 HV,约为基体的3.48倍。熔覆层的摩擦系数和磨损率明显低于基体,磨损率约为基体的1/4。磨损试验过程中在涂层表面生成的大量含氧粘附层出现在涂层表面,有利于提高涂层的耐磨性。     

40Cr钢表面激光熔覆金属陶瓷复合涂层的组织和性能

以WC、TiC、Co以及Co50合金粉末为原料,在40Cr钢表面制备了WC/Co、WC/Co50以及WC-TiC/Co50金属陶瓷复合涂层。使用X射线衍射（XRD）、金相光学显微镜（OM）、扫描电镜（SEM）和EDS能谱,对熔覆层的显微组织和物相构成进行分析。结果表明,在选择适当的激光熔覆工艺条件下,制备的WC/Co50和WC-TiC/Co50复合涂层表面形貌良好,平整连续且无宏观裂纹。硬度测试和摩擦磨损试验表明,复合涂层具有高的硬度（涂层平均显微硬度1126.7 HV0.2以上,涂层表面硬度可达66.2 HRC以上）和良好的耐磨性,其磨损量相比40Cr钢基材分别下降了54%和66%。分析认为,熔覆层硬度和耐磨性提高的原因在于熔覆层中存在大量WC、TiC以及反应生成的W₂C、Fe₃W₃C等碳化物增强相,且均匀分布于基体中。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.     

Microstructures and Mechanical Properties of a Newly Developed Austenitic Heat Resistant Steel

The effect of heat treatment on the microstructures and mechanical properties of a newly developed austenitic heat resistant steel(named as T8 alloy) for ultra-supercritical applications have been studied. Results show that the main phases in the alloy after solution treatment are γ and primary MX. Subsequent aging treatment causes the precipitation of M_(23)C_6 carbides along the grain boundaries and a small number of nanoscale MX inside the grains. In addition, with increasing the aging temperature and time, the morphology of M_(23)C_6 carbides changes from semi-continuous chain to continuous network.Compared with a commercial HR3C alloy, T8 alloy has comparable tensile strength, but higher stress rupture strength. The dominant cracking mechanism of the alloy during tensile test at room temperature is transgranular, while at high temperature, intergranular cracking becomes the main cracking mode, which may be caused by the precipitation of continuous M_(23)C_6 carbides along the grain boundaries. Typical intergranular cracking is the dominant cracking mode of the alloy at all stress rupture tests.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

The 15th Global Foundry Sourcing Conference 2014held in Qingdao China

Organized by Suppliers China Co., Ltd and co-organized by the National Technical Committee 54 on Foundry of Standardization Administration of China, the 15th Global Foundry Sourcing Conference 2014 （hereinafter referred to as FSC 2014） was successfully held on Sep. 23rd in Grand Regency Hotel, Qingdao. More than 500 delegates from home and abroad attended this conference, including over 130 purchasers from 20 countries and 380 domestic and foreign suppliers.     

Secondary Recrystallization Behaviors of Grain-Oriented 6.5 wt% Silicon Steel Sheets Produced by Rolling and Nitriding Processes

By rolling and nitriding processes, 0.23- to 0.3-mm-thick grain-oriented 6.5 wt% silicon steel sheets were produced. The core losses of grain-oriented 6.5 wt% silicon steel at frequencies ranging from 400 Hz to 20 k Hz were lower than that of the grain-oriented 3 wt% silicon steel with the same thickness by 16.6–35.8%. The secondary recrystallization behavior was investigated by scanning electron microscopy, energy-dispersive spectroscopy, and electron backscattered diffraction. The results show that the secondary recrystallization in high-silicon steel sheets develops more completely as the nitrogen content increases after nitriding, secondary recrystallized grain sizes become larger, and the sharpness of Goss texture increases. Because more {110}116 grains in the subsurface and the central layer of the sheets have a lot of 20°–45° high-energy boundaries in addition to Goss grains, {110}116 can be the main component through selective growth during secondary recrystallization when the inhibitor quantity is not enough and inhibitor intensity is weaker. The increases in nitrogen content can increase the inhibitor intensity and hinder abnormal growth of a mount of {110}116 grains and therefore enhance the sharpness of Goss texture.     

Laser Cladded TiCN Coatings on the Surface of Titanium

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs (OM). The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm / s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm - 2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2, and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80?滋m, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis