NbC含量对Ti(C,N)基金属陶瓷组织和力学性能的影响

研究了NbC含量对两种不同Ti(C,N)/TiC质量比金属陶瓷组织和性能的影响。结果表明:随着NbC含量的增长,环形相变得更加完整,粘接相分布越均匀。TiC和NbC含量的不同,影响了溶解和扩散,造成环形相与硬质相的体积分数和元素分布不同。力学性能测试表明,Ti(C,N)/TiC质量比为3︰2、w(NbC)=6%的试样的综合力学性能较好。     

含铌铸铁冶金学基础

论述了铌对铸铁显微组织和性能的影响,铌在铸铁中以NbC形式与奥氏体形成共晶体。在共晶体中NbC呈条形放射状。在铌铸铁中加入钛,形成TiC先于NbC析出,随后NbC围绕TiC结晶,最终形成团块状。     

为V—22飞机开发钛铸件

对钽,铌碳化物工业的发展及生产厂家,中国生产钽,铌碳化物的主要方法,生产的钽,铌碳化物的主要品种和质量标准,钽,铌碳化物的主要应用领域进行了较详细的介绍并展望了中国钽,铌碳化物的发展趋势。     

Mechanochemical synthesis of NbC–NbB2 nanocomposite from the Mg/B2O3/Nb/C powder mixtures

An experimental study was conducted on the preparation and characterization of nanocrystalline niobium boride and carbide composite (NbB₂–NbC) in the Mg–B₂O₃–Nb–C system via mechanochemical method. The thermodynamic appraisal indicated that the reduction and synthesis reactions were highly exothermic and should be self-sustaining. According to the differential thermal analysis (DTA) results, a pre-milling treatment of powder mixture up to 2 h not only reduced the reaction temperature, but also induced a different reaction path. In addition, the amount of Mg₃(BO₃)₂, as a major by-product of the thermal synthesis, was significantly decreased by applying adequate mechanical activation. The phase analysis revealed that the NbB₂ phase was achieved after 3 h high energy ball milling in self-stunning mode; meanwhile, the formation of NbC was progressively completed after a longer period of milling up to 7 h. According to the morphological evolutions, the range of particle size was within 100 nm.     

The effect of nanosized NbC precipitates on electrochemical corrosion behavior of high-strength low-alloy steel in 3.5%NaCl solution

The effect of nanosized NbC precipitates on electrochemical corrosion behavior of high-strength low-alloy (HSLA) steels in 3.5%NaCl solution has been investigated by the means of precipitate modulation, microstructure observation, electrochemical and immersion tests. The results showed that NbC precipitates markedly enhance the corrosion resistance of the H-contained steel, and the mechanism is that the plentiful and highly dispersed nanosized NbC particles acting as massive and effective hydrogen traps play a decisive role in the resistance to hydrogen activated corrosion. Moreover, it is evident that the inhibiting effect is related with the amount, size and distribution of the precipitates, and the optimized microstructures and precipitated phases improve the mechanical properties and resistance to hydrogen activated corrosion of HSLA steel.     

Effect of TiC and NbC carbides on creep life of stainless steels

The effect of TiC and NbC carbides on creep life has been investigated for 321HTB and 347HTB steels at 600–750°C for about 20–200,000 h. The creep data for 304HTB steel are used as reference data. The precipitation hardening is larger for the 321HTB than for the 347HTB at short times during creep. Then the reduction of precipitation hardening due to coarsening of TiC and NbC carbides takes place for up to long times, which is less significant in the 321HTB than in the 347HTB. The smaller coarsening rate of the TiC carbides than the NbC carbides during creep is discussed on the base of a rate equation for diffusion-controlled Ostwald ripening.     

Al对Fe-20Cr-35Ni-0.6Nb合金显微组织和抗氧化性的影响

采用增量法研究了不同Al含量(0.5%、1.5%、2.5%,质量分数)的Fe-20Cr-35Ni-0.6Nb含Nb合金在1000 ℃空气条件下的抗氧化。采用SEM、EDS、TEM、拉曼光谱等手段研究了合金的显微组织和氧化膜特性。结果表明,3种含Nb合金组织为单相奥氏体,基体中存在少量弥散分布的NbC沉淀相,氧化前后沉淀相含量和晶粒大小保持不变。添加0.5%和1.5%的Al后,含Nb合金的表面形成多层结构的氧化膜,最外层和第三层为Cr₂O₃,次表层主要为NiCr₂O₄、NiFe₂O₄和Fe₂O₃,最内层为Al₂O₃内氧化层。基体中的NbC析出相和氧化膜中少量Nb的氧化物(Nb₂O₅)加剧了氧化膜的疏松。当Al含量增加到2.5%时,含Nb合金表面形成连续致密的Al₂O₃氧化膜,降低了Fe-20Cr-35Ni-0.6Nb合金的氧化速率,提高了抗氧化性。     

Gradually varying mechanical properties of in situ synthesized NbC–Fe-graded composite coating

NbC–Fe-graded composite coating was fabricated by in situ synthesis using a pure niobium plate and grey cast iron as the raw materials. SEM analysis demonstrates that the thickness of coating is about 400?μm. From the surface to the matrix, the volume fraction of NbC particulates continuously decreases from 95 to 0%, while the average particulate diameter gradually increases from 200?nm to 1?μm. Along the depth towards the matrix, the nano-hardness and elastic modulus of the graded coating decrease from 23.5 to 3?GPa and from 435 to 150?GPa, respectively. In addition, the fracture toughness (K_C) of 8.62?MPa?m^1/2 is obtained on the surface of the coating by the Vickers indentation technique. And the fracture mechanism is intergranular cracking.     

GH2036合金电渣重熔工艺探讨

通过对GH2036合金电渣重熔工艺的对比分析，发现缓慢熔化有利于消除一次NbC偏析；当熔化速度在6kg／min以上时，出现NbC偏析的机率较大；当熔化速度小于6kg／min时，出现NbC偏析的可能性较小，在某一个合格的熔化速度下可能不会出现NbC偏析，快速提高电流对一次NbC偏析的危害最大.     

中碳铌微合金化钢NbC的析出控制

对开坯+连轧生产出的大规格铌微合金化中碳圆钢的轧后NbC形态进行了研究分析。研究发现,中碳钢铌的质量分数为0.03%时,连铸凝固过程中会析出5 μm以上的碳化铌;钢坯轧制加热温度为1 250 ℃左右,高温段保温时间为4 h以上时,微米级碳化铌得到固溶。