连续冷却过程中GCr15钢中碳化物的析出行为

针对GCr15轴承钢棒材网状碳化物大量析出、网状级别超标问题,通过热模拟试验对碳化物析出机理进行研究。结果表明,GCr15轴承钢试样经热轧后的连续冷却过程中,在晶界处析出的二次碳化物为（Fe.Cr）3C型碳化物,冷却速度对晶界处二次碳化物形貌具有重要影响,随冷却速度的增加,可达到抑制网状碳化物析出并得到高品质轴承钢棒材的目的。     

AISI 316L奥氏体不锈钢低温离子-气体复合渗碳温度对渗碳层的影响

采用离子轰击去除不锈钢表面钝化膜并活化表面,然后在不同的渗碳温度条件下,用氢气和乙炔混合气体对AISI 316L奥氏体不锈钢进行硬化处理,研究了渗碳温度对不锈钢渗碳层组织和性能的影响。结果表明:AISI 316L奥氏体不锈钢低温离子-乙炔气体渗碳的临界温度为540℃。在440~540℃温度范围内,渗碳层中具有单一γc相结构,无铬的碳化物析出,硬化层厚度与硬度均随渗碳温度的升高而增加。当渗碳温度超过540℃,渗碳层中不仅含有γc相,而且会有新相生成(如Cr23C6、Cr7C3、Cr C、Fe3C、Fe2C),从而引起不锈钢耐蚀性能降低。     

Fe-V合金CD渗碳后的组织均匀化

用金相显微镜和扫描电子显微镜分析了Fe—V合金CD渗碳及渗碳加等温处理后的组织。结果表明：Fe—V合金CD渗碳的最佳碳势为1．40％，此碳势为渗层不出现Fe3C的最高碳势。渗层的最表层组织为γ＋V4C3，次表层的组织为α＋V4C3，碳化物颗粒的尺寸随渗层的深入逐渐增大，由表层的250nm增加至2．5μm。渗碳后的等温处理可以使碳化物的颗粒尺寸大大减小，更加均匀，数量明显增多。     

不同热处理对一种高铬铸铁组织的影响

用X射线衍射（XRD）、磁性法和透射电镜（TEM）等方法研究了不同热处理对一种含Mo、Cu高铬铸铁的组织的影响。结果表明：高铬铸铁亚临界处理和去稳处理中,基体会以二次碳化物的形式析出过饱和的碳和合金元素,残余奥氏体发生马氏体转变。在亚临界处理中,处理温度越高,马氏体转变越快;在去稳处理过程中,当温度为1000℃时残余奥氏体量最少,随着处理温度的提高,残余奥氏体反而增多。二次碳化物析出的顺序是首先析出颗粒状的（Fe,Cr）23C6,然后随着保温时间的延长（Fe,Cr）23C6发生原位转变为M3C,基体部分转变为珠光体。     

离子渗碳温度对316L不锈钢渗层组织和性能的影响

利用低温离子渗碳技术.在不同温度下对AISI 316L奥氏体不锈钢进行渗碳处理.利用光学显微镜、显微硬度计、XRD以及电化学测试技术研究了渗碳温度对不锈钢表面显微组织和性能的影响.结果表明,渗碳温度显著影响AISI 316L奥氏体不锈钢渗碳层的组织结构与性能.渗碳温度在400～550℃之间时,可以获得无碳化物析出的、具有单一γ_c相结构的渗碳层;渗碳温度在550℃时,渗碳层为γ相+Cr_(23)C_6+Cr_7C_3+Fe_3C+Fe_2C的混合组织.渗碳层的厚度与硬度均随渗碳温度的升高而增加.550℃是AISI 316L奥氏体不锈钢中铬的碳化物析出的临界温度.为了避免铬的碳化物析出而降低不锈钢的耐蚀性能.奥氏体不锈钢渗碳必须在低于550℃的渗碳温度下进行.     

热加工过程中Ni基变形高温合金析出相的演变规律

变形高温合金在热加工过程中的相析出行为是影响合金抗拉强度的重要因素之一。本实验对GH4738合金在热加工过程中不同阶段的 MC,M23C6,γ′相三种析出相进行跟踪研究。析出相在热加工过程中不同阶段的表现：（1）合金坯料中的主要析出相为初生MC碳化物和初生γ′相。（2）合金经热变形后,初生MC碳化物发生部分分解并析出纳米级晶内次生MC碳化物和少量晶界次生M23C6碳化物,同时析出次生γ′相。（3）合金经热处理后,初生MC碳化物进一步分解直至完全溶解,进而纳米级晶内次生MC碳化物转变为大量酒瓶状晶内次级M23C6碳化物,同时γ′相接近于完全析出,但γ′相会有小幅度的长大。     

钼对含铌低合金铸钢碳化物析出行为的影响

借助熔炼制备合金的方法以及OM、SEM、TEM、碳化物萃取及XRD研究了含铌低合金铸钢中Mo的添加对碳化物析出行为的影响。结果表明:随Mo含量增加,组织由多边形铁素体向针状铁素体转变,片状珠光体向粒状贝氏体转变;铁素体晶粒内弥散析出的颗粒状和随机分布的短杆状碳化物增加,纽扣锭试样的硬度、强度增加,塑性降低。碳化物萃取及XRD衍射分析发现,试样中碳化物质量分数随Mo含量增加而增加;在1#Ori试样中碳化物主要为Fe3C、(Fe,Mn)3C型合金渗碳体及弥散析出的Nb(C,N)颗粒;在2#Mo、3#Mo试样中有Mo2C、Nb(C,N)和Mo(C,N)型碳化物析出。     

金相评级标准系列挂图

应广大会员的要求，全国热处理学会新近出版了一套金相评级系列挂图，内容包括Fe—C和Fe—Fe3C合金相图与热处理温度，Fe—C和Fe—Fe3C合金相图，钢种火花鉴别图，渗碳齿轮碳化物级别图，渗碳齿轮残留奥氏体、马氏体级别图，中碳钢与中碳合金结构钢马氏体等级图，钢件感应淬火金相评级图。全套采用原版金相照片，设计新颖，印刷精美，直观实用。挂图在国际热处理展览会上颇受欢迎，许多热处理专业厂、     

高碳马氏体不锈钢8Cr13MoV球化退火过程中碳化物的演变

利用Thermo-calc软件、扫描电子显微镜（SEM）、透射电子显微镜（TEM）和光学显微镜（OM）等研究了锻造态高碳马氏体不锈钢8Cr13MoV球化退火过程中碳化物的演变。结果表明：锻态组织中存在着M3C、M23C6和M7C3类型的碳化物。球化退火过程中,M3C很快转变为M23C6,M7C3则一直未发生类型转变。升温阶段,组织中马氏体直接分解析出M23C6,没有M3C→M23C6的转变过程。整个退火过程中,析出碳化物均为M23C6型。缓冷阶段降温180 min后组织中碳化物已基本不发生变化,可进一步提高冷却速率。     

渗碳对单晶超合金再结晶性能的影响

单晶超合金DD6的试样经喷砂、液体热处理和在真空气氛中时效处理,然后研究渗碳对单晶超合金DD6再结晶的影响。结果表明渗碳过程中碳渗入喷砂试样中,在喷砂区域生成以亚微米粒子均匀弥散分布的MC型碳化物。这些MC型碳化物再结晶的晶粒边界。随着温度增加,MC型碳化物溶解,析出二次M6C型碳化物。在M6C型碳化物和再结晶的晶粒边界之间的相互作用进一步阻碍再结晶。     

PROCESS OF CARBIDE PORMATION DURING AUSTENITEPEARLITE TRANSFORMATION IN CHROMIUM STEELS

研究了四种高铬钢在恒温分解为珠光体时的碳化物形成过程。对所得结果和其他作者的结果进行了分析,得到统一的规律。 在铬钢中,珠光体转变时可以直接形成(Fe,Cr)_3C,(Cr,Fe)_7C_3或(Cr,Fe)_(23)C_6。但是,不同类型碳化物的形成并不决定于平衡图上所要求的碳化物类型,而决定于奥氏体中的Cr:C比值。Cr:C比值对碳化物成核的过程起着主导的作用。     

热处理工艺对离心铸造高铬铸铁轧辊组织及硬度的影响

采用了光学显微镜、扫描电镜、X射线衍射仪、洛氏硬度计等仪器,研究了离心铸造高铬铸铁轧辊铸态及淬火与回火后的显微组织结构、碳化物和硬度等。结果表明:高铬铸铁轧铸态组织主要是由奥氏体+少量马氏体+(Cr,Fe)₇C₃碳化物组成,碳化物呈粗大板条状或块状,不同温度热处理后,得到回火马氏体+(Cr,Fe)₇C₃+Cr₇C₃碳化物的组织,组织中粗大板条状碳化物消失,得到细小块状或椭圆状碳化物。该高铬铸铁轧辊铸态硬度为56.0HRC左右,在950℃淬火及400℃回火处理后硬度增加到了约65.5HRC。     

Fiber laser welding of WC-Co to carbon steel using Fe-Ni Invar as interlayer

A fiber laser procedure was developed for joining cemented carbides to carbon steels (3-mm-thick plates) in the butt joint configuration using fcc Fe-Ni invar as interlayer. The optimized welding parameters gave a required weld width and penetration. The as-welded microstructure was characterized as a function of welding speed through fiber laser welding. In fusion zone, non-equilibrium fcc (γFe, Ni) was the predominant phase with α-WC and some mixed carbides such asFe₃W₃C and Co₆W₆C. In heat affected zone (HAZ) of cemented carbide, the phases consisted of α-WC, (γFe, Ni) and mixed carbides. Bct–martensite was observed in HAZ near steel side. Which were confirmed by XRD, TEM, and nickel-iron phase diagram calculate using Thermo Cal Classic software. Thick and large sized η-phases were inhibited in the HAZ of cemented carbide and replaced by η-phases with carbon depletion. A higher energy input produced more non-equilibrium (γFe, Ni) and martensite. Small amounts of η-phases, non-equilibrium (γFe, Ni) besides the martensite. The thermal cycles associated with laser welding led to a rather small fusion zone, which usually inhibited η-phases formation due to the inhibition of normal grain growth and the decrease of iron/nickel diffusion across WC/Co interface. The results indicated that the maximum bend strength was 980.90MPa. Due to the formation of martensite/carbides and an excess of which led to embrittlement, welded-joint samples were broken at the HAZ or in the fusion zone instead of the base metal. The cracks exhibited the characteristics of hot crack ((γFe, Ni) in the fusion zone) and cold crack (α-WC at the HAZ of cemented carbide).     

电冶稀土WC钢结硬质合金中碳化物特征的研究

采用电渣熔铸冶金工艺，用回收的碳化钨钢结硬质合金作原料，再加入微量的稀土，制备了新型的钢结硬质合金。用透射电镜、扫描电镜、金相显微镜及X射线衍射等测试手段研究了新材料中的碳化物的特征。结果表明：在该材料的显微组织中存在原始颗粒区和扩散区。原始颗粒区组织中碳化物的特征是存在大量变化甚微的角状大尺寸原始WCp及具有明显反应层的长椭圆状WC颗粒，界面反应产物为Fe3W2C。在粗大碳化钨颗粒附近能够原位生成先共晶析出相（WC和W2C），在较远处的钢基体中分布着细网状碳化物，同时有（Cr，Fe）7C3等条状复式碳化物生成；而扩散区主要细小W2C小颗粒、WC颗粒及再结晶W-Fe-C小颗粒组成。稀土的加入可提高WC颗粒分散性。     

Catalytic Effect Analysis of Metallic Catalyst During Diamond Single Crystal Synthesis

By transition metals （Fe, Ni, Mn, Co） and their alloys as catalysts during the diamond synthesis, some transition phases will be formed, such as FeaC type carbides and y solid solutions. Based on the empirical electron theory of the solid and molecules, the valence electron structures of different kinds of carbides and y solid solutions and the relative electron density differences of various diamond/carbide and y solid solution/carbide interfaces were calculated and analyzed in this paper. The electron structure conditions of the ideal catalyst were presented by analyzing the different catalytic effects of the catalysts, which provide a new theoretical path to the optimal design of the catalyst composition     

离心铸造WC/钢复合材料显微组织

采用离心铸造工艺制备了以废弃的轴承钢GCr15为基体,WC颗粒为硬质相的WC/钢复合材料.用金相观察和X射线衍射等分析方法,对该材料的显微组织进行了研究.结果表明:离心铸造WC/钢复合材料的显微组织是由莱氏体(P+Fe_3C_Ⅱ(共晶))、一次渗碳体(Fe_3C_Ⅰ)、二次渗碳体(Fe_3C_Ⅱ)、合金渗碳体((Fe,M)_3C)等碳化物及粒状珠光体组成,且其中有大量细小的WC、W_2C、再结晶W-Fe-C颗粒以及M_6C、M_7C_3、M_(23)C_6等碳化物颗粒析出;碳化物的形态较多,主要有网状、鱼骨状、树枝状和条块状.     

Carbide Precipitation in Austenite of a Titanium-Tungsten-Bearing Low-Carbon Steel

In this study, the carbide precipitation at 925 °C in austenite (γ) of a 0.04C-1.5Mn-0.10Ti-0.39 W (wt%) low-carbon steel was investigated by stress relaxation (SR) high-resolution transmission electron microscopy and atom probe tomography. First-principles calculations were employed to reveal the precipitation mechanism. Results indicate that a high dispersion of W- and Fe-rich MC-type ultrafine carbides (< 10 nm) forms during the very early stage prior to the onset of precipitation determined by SR. These ultrafine carbides possess a B1-crystal structure with a lattice parameter of 3.696 Å, which is quite close to that of γ (3.56 Å). It can significantly decrease the misfit of carbide/γ interface with a cube-on-cube relationship, thus assisting the carbide nucleation. As the time prolongs, a few spherical or polygonal Ti-rich (Ti, W)C particles (18-60 nm) are formed at the expense of the ultrafine carbides by nucleation and growth on them. These (Ti, W)C particles are identified with a “core-shell” structure (Ti-rich core and Ti, W-rich shell), which leads to a better-coarsening resistance compared with pure TiC in Ti steel. Calculation results show that the composition and structure of carbides at certain stage are closely related to a combined effect of W, Fe, and Ti atoms together with interstitial vacancies.     

Combination of TEM and 3D atom probe study of microstructure and alloy carbide in a Nb-V micro-alloyed steel tempered at 650 °C

3D atom probe (3DAP) combined with TEM is applied to characterize the nanostructure and composition of coarsening carbides that precipitate in a Nb-V micro-alloyed steel tempered at 650 °C for 4 h. The results indicate that high temperature tempering of the as-quenched lath-like martensitic structures leads to the coarsening of alloyed carbide in the recovered ferritic matrix. TEM characterization and EDS analysis show that the alloy carbides are typically spherical or ellipsoidal and are enriched with V, Nb and Mo. Crystallographic lattice overlap and distortion create a distinct optical Moiré pattern at the carbide/matrix boundary, as observed by HRTEM. 3DAP gives the compositional distribution at atomic scale in the coarsening carbide and the surrounding matrix. Non-carbide-forming elements such as Si and Al are depleted in the carbide and are enriched at the carbide/matrix heterophase interface. Carbide-forming elements such as Mn, V, Mo and Nb distribute heterogeneously in the whole carbide, leading to the formation of a Mn-, V- and Mo-enriched core and Mo-enriched external shell.     

Effect of Co on Microstructure and Stress Rupture Properties of K4750 Alloy

The effects of substituting Co for Fe on the microstructure and stress rupture properties of K4750 alloy were studied.The microstructure of the alloy without Co(K4750 alloy) and the alloy containing Co(K4750-Co alloy) were analyzed.Substitution of Co for Fe inhibited the decomposition of MC carbide and the precipitation of η phase during long-term aging treatment.In K4750-Co alloy,the morphology of MC carbide at the grain boundary(GB) remained dispersed blocky shape and no η phase was observed after aging at 750℃for 3000 h.However,in K4750 alloy,almost all the MC carbides at GBs broke down into granular M_(23)C_6 carbide and needle-like η phase.The addition of cobalt could delay the decomposition of MC carbides,which accordingly restricted the elemental supply for the formation of η phase.The stress rupture tests were conducted on two alloys at 750℃/430 MPa.When Co is substituted for Fe in K4750 alloy,the stress rupture life increased from 164.10 to 264.67 h after standard heat treatment.This was mainly attributed to increased concentration of Al,Ti and Nb in γ' phase in K4750-Co alloy,which further enhanced the strengthening effect of γ' phase.After aging at 750℃for 3000 h,substitution of Co for Fe can also cause the stress rupture life at 750℃/430 MPa to increase from 48.72 to 208.18 h.The reason was mainly because MC carbide degradation and η phase precipitation in K4750 alloy,which promoted the initiation and propagation of micro-crack during stress rupture testing.     

回火马氏体中合金碳化物的3D原子探针表征Ⅲ.粗化

Nb-V微合金钢在1200℃固溶0.5 h后淬火,在650℃回火4 h,利用SEM和HRTEM观察显微组织,合金碳化物的形貌特征和精细结构,用三维原子探针(3DAP)研究合金碳化物中元素分布规律.结果表明,淬火微合金钢在650℃回火4 h后,马氏体板条内位错和板条界面因回复而消失,粗化的合金碳化物分布在原马氏体板条界面和板条内部.同时,伴随着合金元素的再分配,早期析出的圆盘状碳化物沿厚度方向生长,出现一个与基体(M_(bcc))和原碳化物(P_(inner))成半共格关系的新生过渡相(P_(outer)).非碳化物形成元素Si和Al主要分布在碳化物/基体界面处;V和Mn主要分布在碳化物内层,而Mo和Nb分布在整个碳化物区域.粗化的碳化物是一种具有核心和外壳结构的合金碳化物,内层主要是V-Mn-Mo-Nb的碳化物,而外层主要是Mo-Nb的碳化物.