8Ci20Si2Ni马工体汽阀钢的碳化物

研究了电炉工艺和电渣工艺生产的８Ｃｒ２０Ｓｉ２Ｎｉ钢中碳经物类型、形貌、分布特征及其室温性能随温度的变化。在Ｐｈｉｌｉｐｓ ＣＭ１２电子显微镜中观察到１０５０℃加热时晶内块状和症状Ｍ２３Ｃ６数量最多，尺寸最大，冷却时原奥氏体晶界块状Ｍ２３Ｃ６之间还析出少量精细颗粒和薄片Ｍ７Ｃ３；随着加热温度的升高，块状Ｍ２３Ｃ６数量减少，粒状Ｍ２３Ｃ６精细颗粒和薄片枝晶Ｍ７Ｃ３的数量增多，在高于１１５０℃加热和加     

5Cr21Mn9Ni4N（21—4N）钢中M23C6的沉淀

观察研究了２１４Ｎ钢中球（块）状Ｍ２３Ｃ６,特别是球间片状Ｍ２３Ｃ６的沉淀特征。发现球（块）状Ｍ２３Ｃ６的数量、尺寸不仅取决于固溶效果Ｐ值,而且还与固溶加热后的冷却速度有关;球间片状Ｍ２３Ｃ６的沉淀倾向较大,其沉淀倾向对固溶加热后的冷却速度十分敏感,冷却速度的减慢相当于固溶温度的降低;Ｐ值愈大或冷却愈慢,片状的数量愈多;反之,薄片的尺寸和厚度愈小     

MICROSTRUCTURES AND PROPERTIES OF DZ40M Co-BASE SUPERALLOY AFTER LONG-TERM AGEING AT 950℃

研究了新近开发的一种定向凝固钴基高温合金ＤＺ４０Ｍ９５０℃长期时效后的组织与性能。结果表明,合金时效后室温强度提高,塑性降低,９８０℃,８３ＭＰａ持久性能提高,而８１６℃,２１５ＭＰａ持久性能下降,在时效过程中,初生碳化物Ｍ７Ｃ３和ＭＣ缓慢分解,细小的Ｍ２３Ｃ６在基体中大量析出,Ｍ６Ｃ在一些Ｍ７Ｃ３表面生成。分析认为,合金性能变化主要归因于Ｍ２３Ｃ６沉淀析出,初生碳化物Ｍ７Ｃ３和ＭＣ分解,释放出碳     

DM7新型工具钢的组织与性能

研究了ＤＭ７新型工具钢的组织与性能。结果表明，ＤＭ７钢的退火组织为球状珠光体，淬火温度以９００～９５０℃为宜，淬火组织为马氏体＋残留奥氏体＋碳化物，碳化物类型有Ｆｅ３Ｃ，Ｍ２３Ｃ６，Ｍ６Ｃ及ＶＣ，回火温度不应高于３００℃，ＤＭ７钢比６ＣｒＷ２Ｓｉ钢硬度高２ＨＲＣ，屈服强度高２０％，耐磨性高６０％。     

8Cr20Si2Ni马氏体汽阀钢的碳化物

研究了电炉工艺和电渣工艺生产的8Cr20SiZNi钢中碳化物类型、形貌、分布特征及其室温性能随温度的变化。在Philips CM12电子显微镜中观察到1050℃加热时晶内块状和粒状M_(23)C_6数量最多,尺寸最大,冷却时原奥氏体晶界块状M_(23)C_6之间还析出少量精细颗粒和薄片M_7C_3;随着加热温度的升高,块状M_(23)C_6数量减少,粒状M_(23)C_6 精细颗粒和薄片枝晶M_7C_3的数量增多,在高于1150℃加热和加热后的冷却过程中,枝晶薄片和精细颗粒M_7C_3聚集长大、增多。     

铁基合金激光熔覆组织及高温时效转变的TEM研究

利用ＡＴＥＭ研究了铁基多元合金ＦｅＣｒＷＮｉＣ激光熔覆层的微观组织、亚稳相结构特征以及高温时效时的亚稳相转变机制。结果表明组织为亚共晶组织,即γ＋（γ＋Ｍ７Ｃ３）,γ奥氏体为具有较高合金度的过饱和亚稳相,Ｍ７Ｃ３（Ｍ为Ｃｒ,Ｆｅ,Ｗ）为六方结构的Ｃｒ基亚稳合金碳化物。熔覆组织在高温时效时存在两类碳化物形成机制,即亚稳γ中析出Ｍ２３Ｃ６、Ｍ２Ｃ与ＭＣ碳化物以及Ｍ７Ｃ３→Ｍ２３Ｃ６与Ｍ７Ｃ３→Ｍ６Ｃ的碳化物原位转变机制。熔覆组织具有较高的显微硬度并存在显著的二次硬化特征     

高速钢中碳化相的恒电位单相显示

利用恒电位浸蚀与伏安法研究了高速钢中碳化物相Ｍ６Ｃ，ＭＣ，Ｍ２３Ｃ６１（Ｍ７Ｃ３）的单相浸蚀条件。它可作这些碳化物观察和鉴定。     

21—4N钢的过热与锻造裂纹

２１－４Ｎ钢在１２１０￣１２５０℃加热时，不同程度地出现晶粒粗化，晶界被Ｍ２Ｎ和Ｍ７Ｃ３弱化的过热组织特征，温度愈高，过热程度愈大。过热后，不适当的锻造另工温度促使锻造裂纹的形成，锻造裂纹起源于锻坯表面，沿大晶粒间界扩展。     

2Cr12NiMoWV铜的回火转变

研究了２Ｃｒ１２ＮｉＭｏＷＶ钢淬火后,经３５０～７１０℃不同温度回火,其显微组织、相结构和室温力学性能的变化。结构表明：在４００～５００℃回火,出现回火,出现回火脆性,这主要与马氏体中析出Ｍ２Ｃ、Ｍ２３Ｃ６型碳化物,产生二次硬化有关。在５５０～５７０℃回火,出现冲击韧度明显升高的现象,升高值与淬火温度有关。随回火时间的延长,发生了Ｍ７Ｃ３→Ｍ２３Ｃ６碳化物类型的转变。     

碳铬共渗奥氏体不锈钢的组织结构

采用透射电镜和Ｘ射线衍射技术研究了奥氏体不锈钢碳铬共渗层的组织结构。结果表明：在碳铬共渗过程中，先在渗层中形成Ｃｒ＿（２３）Ｃ＿６型碳化物，它与母相奥氏体（Ａ）之间具有的取向关系。进一步提高表面碳含量可生成Ｃｒ＿７Ｃ＿３型碳化物。表面碳含量越高，所生成的Ｃｒ＿７Ｃ＿３碳化物越多，而Ｃｒ＿（２３）Ｃ＿６型碳化物则减少。碳铬共渗层由表及里的最终组织为：Ａ＋Ｃｒ＿７Ｃ＿３→Ａ＋Ｃｒ＿７Ｃ＿３＋Ｃｒ＿（２３）Ｃ＿６→Ａ＋Ｃｒ＿（２３）Ｃ＿６     

热处理工艺对新型系泊链钢组织与耐蚀性能的影响

采用920℃水冷淬火后再经560～650℃保温3 h的回火工艺,研究了不同回火工艺对新型系泊链钢组织、耐蚀性能的影响。结果表明,该新型系泊链钢随回火温度从560℃升高到650℃,碳化物析出类型由低温的M3C型向高温的M7C3和M23C6型转变;形态由低温细小棒状和片状逐渐向高温颗粒较大椭圆状和球状转变;耐蚀性能逐渐变好,应力腐蚀敏感性也逐渐减小。耐蚀性能的变化主要是由回火组织中相界、晶界及碳化物的数量和形态的变化所引起的。     

Microstructures and Hardness of 8CrWMoV Steel with Multiple Types of Ultra Fine Carbides

The structure and hardness of 8CrWMoV steel with multiple types of ultra fine carbides are studied after annealing, quenching and tempering in this paper. The results show that multiple types of carbides M3C, M7C3, M23C6, M6C and MC were observed in the annealed steel. Nucleation and coalescence of new carbides, partial dissolution of original carbides in 7 phase region during annealing at 800-840℃, result in ultra-fine carbides. Average size of the carbides is 0.33～0.34μm in the steel annealed at 800～840℃. Because M3C and M23C6 dissolve easily in austenite, the high hardness HRC63～65 can be obtained by quenching at 840～860℃. Un-dissolved carbides M6C and MC (VC) can effectively prevent the coarsening of austenitic grain, and conduce to obtain very fine martensite. The retained austenite can be easy to decompose during tempering at low and middle temperature due to the precipitation of multiple types of carbides and the good tempering-resistance of the steel is obtained. The microstructure and property of the steel after heat treatment can be accurately explained by calculating based on phase equilibrium thermodynamic.     

高CoNi合金钢中二次碳化物的析出与转化

高CNi超高强度合金钢是典型的淬火回火马氏体钢,等温回火处理产生的针状合金碳化物沉淀即二次硬化反应使材料达到高的强韧性,针状合金碳化物M2C从马氏体基体α-Fe中以共格形态析出,该共格关系随过时效而失去回火温度较高时M2C转化为稳定的合金碳化物M23C6和M7C3。利用微衍射技术唯一地确定了可能的合金碳化物沉淀相的晶体结构。     

Effect of Indirect Transformation of Retained Austenite During Tempering on the Charpy Impact Toughness of a Low-Alloy Cr-Mo-V Steel

A modified tempering treatment has been designed in order to avoid the direct transformation of retained austenite (Ar) during tempering of a low-alloy Cr-Mo-V steel. Instead of the direct transformation of Ar into ferrite and M₂₃C₆ carbides during conventional tempering at 700 °C, transformation into aggregate of ferrite and cementite has been forced by a pre-tempering at 455 °C before conventional tempering. Experiments have been performed on specimens quenched with cooling rates 1.5, 3 and 12 °C/s, providing different types of Ar within the as-quenched microstructures. The results show that the tempering modification does not improve the Charpy impact toughness at the highest quenching rate of 12 °C/s, where the specimens cannot incur cleavage cracking induced from fine and discontinuous M₂₃C₆ carbides along lath interfaces. For the lowest quenching rate 1.5 °C/s, the Charpy impact toughness can be improved, and the failure is dominated by carbide aggregates, which originate from the decomposed products of blocky Ar. This is because the tempering modification effectively suppresses the formation of coarse M₂₃C₆ carbides at interfaces between the carbide aggregate and bainitic matrix, thereby resulting in a relatively homogeneous distribution of M₂₃C₆ carbides inside carbide aggregates. Therefore, the tempering modification is recommended for large-scale forgings, in which relatively high quenching rates are difficult to achieve.     

H13钢退火态中的碳化物分析

H13热作模具钢在850℃保温2 h后,以25℃/h速度缓慢冷却至室温。用SEM观察合金组织经球化退火处理后的形态变化,用EDS、XRD、TEM和萃取分离方法对H13钢退火态中碳化物进行了定性和定量分析。结果表明,经850℃球化退火处理后,合金中原有的马氏体组织和珠光体组织基本转化成球状碳化物,主要碳化物类型有4种:MC、M6C、M7C3、M23C6,而且不同类型的碳化物所含的主要合金元素不同,MC中的主要合金元素为V,M7C3和M23C6中的主要合金元素为Cr,M6C中的主要合金元素为Mo和Cr。     

硼含量对镍基合金GH4049晶界析出相和高温性能的影响

在晶界面上用萃取碳复型技术研究了镍基合金GH4049(Ni-15Co-10Cr-5．5W-5Mo-4．2Al-1．5Ti)中与B和C的晶界偏聚效应密切相关的二次析出相特征．B含量低于0．008％时,因固溶B／C(原子比)很低,晶界析出大尺寸MC薄膜和M6C枝晶片以及薄膜状M23C6,不利于高温塑性和持久寿命．B含量为0．011％和0．018％时,固溶B／C(原子比)虽仅为0．667和0．941,已可减少和全部抑制上述碳化物的析出,代之以弥散M3B2颗粒,高温性能大幅度上升．但B含量过高,M3B2密集析出,高温性能下降．降低固溶冷却速度而使B和C原子向晶界长程偏聚,可促进M3B2析出,改善MC的形貌并抑制M6C和M23C6析出。     

Semisolid structure for M2 high speed steel prepared by cooling slope

Effects of cooling slope angle and the temperature of molten metal on the globular structure of M2 high speed steel after holding at the semisolid state have been investigated. The globular structure was achieved by pouring the molten metal at 1595 °C on the ceramic cooling slope with the length of 200 mm and the angle of 25°. The globular structure of M2 high speed steel in the form of rolled–annealed and as cast condition after holding at semisolid state has been achieved. The size of globular grains of cooling slope sample was smaller than that of the rolled–annealed and as cast samples. Solid particles of rolled–annealed sample after holding at semisolid state had better roundness compared with cooling slope sample. Dissolution of carbides in the austenite phase at grain boundaries leads to formation of globular particles in the semisolid state. MC-type and M₆C-type eutectic carbides reprecipitate during cooling cycle along grain boundaries.     

HP40裂解炉管组织及裂纹产生原因分析

本文用SEM、EDS、XRD对开裂的HP40裂解炉管进行分析,发现多数裂纹均位于焊缝附近,且均沿枝晶间和晶界开裂的碳化物扩展.经EDS成分分析和XRD结构分析,这些开裂的碳化物为M23C6和富Nb、Si的碳化物.新炉管组织为奥氏体和枝晶间分布的M7C3及高Nb、Si的共晶碳化物.新旧炉管比较可知,开裂炉管的结构和形态在长时间高温下均发生了明显变化,即M7C3转变为M23C6且明显粗化,在晶界呈连续分布.这种脆而硬的碳化物在组织应力和热应力作用下碎裂成为潜在的裂纹源,它们加速了裂纹扩展进程,缩短了炉管的使用寿命.沿裂纹打开断口发现,整个断面被这两种碳化物所覆盖.这进一步证实了造成裂解炉管早期开裂的原因是这种沿晶界连续分布的粗大碳化物的存在.     

20Cr高铬铸铁离心铸造铸态组织

对20Cr高铬铸铁离心铸造后的铸态组织进行了观察。结果表明：在离心铸造条件下,20Cr高铬铸铁的铸态组织为马氏体＋M7C3型碳化物＋残余奥氏体＋M23C6型碳化物。上述组织的形式与实际冷却条件有关。