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 研究了890~1040 ℃加热淬火对超高强度钢未溶碳化物及力学性能的影响。结果表明：淬火加热温度上升到约1010 ℃,其奥氏体晶粒的长大还没有使板条马氏体束尺寸增加到明显降低钢的强度和韧性时,未溶碳化物MC含量却显著下降,使实验钢的冲击韧性达到峰值。     

碳含量对4Cr5Mo2V型热作模具钢冷热疲劳性能的影响

采用自约束热疲劳试验法,结合SEM、EDS以及Jmat-pro热力学计算软件等研究了碳含量(0.35%和0.71%)变化对4Cr5Mo2V型热作模具钢冷热疲劳性能的影响。结果表明:提高含碳量后,钢中析出大量细小弥散的MC型碳化物,从而使0.71%C钢的抗回火软化性能和热稳定性能均强于0.35%C钢;冷热疲劳循环1000次后,提高碳含量推迟了疲劳裂纹的萌生,当循环次数增加到2000次后,虽然0.71%C钢表面和基体的软化程度均弱于0.35%C钢,但该钢存在较多尺寸较大且呈聚集状态分布的未溶碳化物,这些碳化物在应力的作用下与基体脱离,脱离处成为裂纹扩展的通道,从而促进了疲劳裂纹萌生和扩展。     

不同类型碳化物在基体中的分布对高速钢轧辊性能的影响

通过对具有不同组织的两种进口高速钢轧辊及一种国产辊环进行冷热疲劳试验及摩擦磨损试验,研究了不同类型碳化物在基体中的分布对高速钢轧辊性能的影响。结果表明,在晶界处分布的大块未溶共晶碳化物周围容易萌生裂纹,且大块的未溶共晶碳化物在经过多次冷热疲劳循环后容易碎裂并脱落,在磨损过程中,大块未溶共晶碳化物同样容易发生碎裂及脱落现象,大大影响耐磨损性能;裂纹容易沿晶界处分布的碳化物扩展,且晶界处分布大块的未溶共晶碳化物或碳化物联结成网状容易促进裂纹的扩展;晶界处M2C型碳化物与晶界成一定角度分布,具有一定阻碍裂纹扩展的作用;不同类型碳化物在基体中的弥散分布对于提高其耐磨性能具有很大作用。     

预处理工艺对W6Mo5Cr4V2高速钢组织与性能的影响

研究了预处理工艺对Ｗ６Ｍｏ５Ｃｒ４Ｖ２高速组织与性能的影响。试验结果表明，与退火预处理相比，调质预处理的奥氏体晶粒细小，未溶碳化物少，残留奥氏体量多，屈服强度高，低应力区疲劳寿命长，但抗弯强度，塑性，冲击韧度，断裂韧性都较低，高应力区疲劳寿命也短。     

Co对4Cr5Mo2V钢组织和强韧性的影响

采用OM、SEM、EDS、硬度测试、室温冲击及高温拉伸等方法研究了Co对4Cr5Mo2V钢的组织和强韧性的影响。结果表明:经1010 ℃淬火30 min,4Cr5Mo2V-Co钢未溶碳化物数量更多,马氏体板条更细;510~600 ℃回火时,4Cr5Mo2V-Co钢的回火硬度较4Cr5Mo2V钢高出1~2 HRC,但二者冲击性能相当;相同初始硬度条件下,4Cr5Mo2V-Co钢具有更高的高温强度,这是因为Co元素的添加促进了4Cr5Mo2V-Co钢二次硬化碳化物的形核速率,并能降低碳化物的粗化速率,从而提高了4Cr5Mo2V-Co钢的强度。     

元素V对奥氏体焊缝金属晶间腐蚀敏感性的影响

采用透射电镜(TEM)分析技术研究了1Cr19Ni23N焊条熔敷金属中钒含量对组织及对熔敷金属抗晶间腐蚀性能的影响.结果表明,低钒含量焊条熔敷金属组织中沿奥氏体晶界析出M23C6型富铬碳化物,在晶界附近形成贫铬层,导致晶间腐蚀的发生;高钒含量焊条熔敷金属组织中,V优先于Cr与C形成细小弥散的碳化钒分布在晶粒内部,使得该焊条在保持原较高碳含量的基础上,通过改变碳化物形态和分布达到了保持高强度和改善晶间腐蚀敏感性的目的.     

回火温度对锯片用复合钢板组织性能的影响

对45Mn2V/Q345复合锯片用钢进行了系列温度的回火处理,测定了试验钢的强度与伸长率,并观察了其显微组织,分析了回火温度对复合钢板组织及拉伸性能的影响。结果表明:45Mn2V覆层淬火后得到针状马氏体,Q345钢基板形成板条马氏体。回火温度在400 ℃以下时,45Mn2V钢组织中析出的碳化物细小且弥散,超过400 ℃后则明显粗化,达到480 ℃时粗大的碳化物大量析出,导致试验钢的强度先随回火温度的升高而降低,但在480 ℃时有明显的增加。基板组织在回火过程中则主要发生马氏体板条的合并粗化,达到480 ℃后开始出现等轴的再结晶晶粒,但这一变化未能改善复合钢板的塑性。     

钒对高铬合金铸渗层组织与性能的影响

通过真空实型铸造工艺(V-EPC)在ZG45钢表面制备不同含钒量的高铬合金复合层,采用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)分析了含钒量对铸渗层组织的影响,使用洛氏硬度计和冲击磨损试验机研究了钒含量对硬度和耐磨性的影响。研究表明,铸渗层组织主要由α-Fe与α-Fe+M₇C₃+VC共晶组织组成,过渡层内各合金元素成梯度分布,C、Cr、V元素自铸渗层向基体发生了扩散,且C、Cr、V元素的分布与碳化物的分布高度重合。随着钒含量的增加,晶粒逐渐细化,共晶碳化物数量逐渐增多,VC也增多,铸渗层硬度和耐磨性显著提高。热处理后有大量二次碳化物析出,随着铸渗层中钒含量增加,热处理后二次硬化效果显著提高。     

球磨机ZGMn13衬板的失效分析

采用化学成分分析、金相检验等方法,对高锰钢衬板在使用中的碎裂进行分析.分析表明,衬板中存在严重的疏松,晶界上有大量未溶块状碳化物并析出针状碳化物以及球状氧化物;热处理工艺不当、铸造疏松以及非金属夹杂物的超标是导致球磨机衬板早期失效的主要原因,并提出了改进措施.     

Influence of carbides morphology on the mechanical properties for Fe-C-V alloys

The paper presents the results of tests on the spheroidising treatment of vanadium carbides VC done with magnesium master alloy and RE. The conducted metallographic studies have shown that introducing the magnesium master alloy to an Fe–C–V system of eutectic composition causes the crystallisation of spheroidal carbides. The content of these carbides is about 5.6%, representing 33% of all the crystallised vanadium carbides. Adding RE to the base alloy melt caused 31% of the vanadium carbides crystallise as dendrites. Testing of mechanical properties has proved that the spheroidising treatment of VC carbides in high-vanadium cast iron increases the tensile strength by about 60% and elongation 14–21 times, depending on the type of the spheroidising agent used. Tribological studies have shown that high-vanadium cast iron with eutectic, dendritic and spheroidal carbides has the abrasive wear resistance more than twice as high as the abrasion-resistant cast steel.     

铸铁铬硅共渗渗层组织特征及形成机制

采用固气法对铸铁铬硅共渗渗层的组织特征和形成机制进行了分析和探讨。显微分析表明，渗层由ａ相和Ｃｒ＿７Ｃ＿３、Ｃｒ＿２３Ｃ＿６等碳化物组成，其外表面富集的铬含量可达３０％以上，不含石墨。渗层下面为含大量珠光体的过渡区，靠近表面的渗层里，可观察到包围石墨的白亮环区。该环区很可能是因共渗过程中Ｃｒ、Ｓｉ原子在石墨周围局部聚集而形成的。保温时间延长，环内石墨消失，但仍保留环区特征。这种组织结构提高了铸铁的抗蚀能力及抗高温氧化能力。     

Microstructures and Mechanical Properties of Bearing Steels Modified for Preparing Nanostructured Bainite

Mo containing high-C-Cr bearing steel was modified with Si (0.8–1.5 wt.%) and 0.8Si–1.0Al to prepare nanostructured bainite by low-temperature isothermal heat treatment. The modified steels were isothermal held at 220 to 240 °C after partial austenitization in an intercritical gamma+carbide region, and the resultant microstructure and mechanical properties were studied. Carbide-free nanostructured bainite with plate thickness below 100 nm and film retained austenite, as well as a small amount of undissolved carbide particles, was obtained in the modified steels except in 0.8Si steel, in which carbides precipitated in bainitic ferrite. As Si content increased, the mean thickness of bainitic ferrite plates modestly decreased, whereas the fraction of retained austenite markedly increased. The thickness of bainitic ferrite plate and the fraction of retained austenite in Si-Al-modified steel were smaller than those in Si-modified steels. The hardness and elongation of the Si-Al-modified steel were lower than those of Si-modified steels. The yield strength of Si-Al-modified steel was superior to that of Si-modified steels. Mid-level ultimate tensile strength and impact toughness were achieved in Si-Al-modified steel. For bearing applications, Si-modified steels could provide higher hardness and toughness but lower dimensional stability. Meanwhile, Si-Al-modified steel could offer higher dimensional stability but lower hardness and toughness.     

Enhancement of wear resistance and impact toughness of as cast hypoeutectic high chromium cast iron using niobium

The effect of niobium additions on the as-cast microstructure of a hypoeutectic high-Cr cast iron containing 2.2 wt.% C and 16.5 wt.% Cr was investigated. With increasing niobium content, the eutectic M₇C₃ carbides were refined and became less elongated as well as its volume fraction was decreased gradually. The first precipitated NbC particles could be act as heterogeneous substrate of proeutectic austenite and a barrier to M₇C₃ grain growth. The morphology of NbC carbides changed with increasing niobium content. Such NbC particles were increased with increasing Nb content and subsequently contributed to increased hardness. Optimum toughness was obtained for the irons alloyed with 2.14% Nb. The effects of applied load and Nb-additions on wear resistance of high chromium cast iron have been studied. The results showed that wear resistance increases with increasing Nb addition. Furthermore, the effectiveness of the NbC particles on the weight loss was more evident at higher loads.     

铝元素抑制超高碳钢中网状碳化物析出机理

借助相图计算、能谱分析及组织观察研究了铝元素对超高碳钢中网状碳化物析出过程的影响,含碳1．5wt％的超高碳钢添加不同含量的铝后显著影响网状碳化物的析出：随铝含量增加,奥氏体晶粒尺寸愈小、晶界愈多,导致网状碳化物减薄;未溶碳化物愈多、奥氏体固溶碳含量愈少,导致网状碳化物析出量减少;晶界聚集铝量增加,聚集的铝抑制碳化物的形核及长大。当铝含量接近2．0wt％时,网状碳化物出现断续,甚至有的晶界没有碳化物析出,在球化过程中,该网状碳化物很容易球化。     

Microstructure and mechanical properties of WC Ni–Si based cemented carbides developed by powder metallurgy

In this paper the influence of the Ni binder metal and silicon as an additional alloying element on the microstructure and mechanical properties of WC-based cemented carbides processed by conventional powder metallurgy was studied. Microstructural examinations of specimens indicated the presence of a very low and even distributed porosity and the presence of islands of metal binder in the microstructure of the cemented carbides. Furthermore, despite the addition of silicon and carbon in the cemented carbides, it was not observed the presence of small fractions of undissolved SiC and free graphite nodules in their microstructure. Vickers hardness and Flexural strength tests indicated that the cemented carbide WC–Ni–Si with 10 wt.% of binder presented bulk hardness similar to the conventional WC–Co cemented carbides and superior flexure strength and fracture toughness.     

Mo对高强度钢延迟断裂行为的影响

在含V和Nb的40Cr钢中添加不同质量分数(0-1．54％)的Mo元素,采用缺口拉伸试样和改进的M—WOL型试样研究了Mo对高强度钢延迟断裂行为的影响．结果表明,随着Mo含量的增加,实验钢的延迟断裂抗力逐渐提高;当Mo含量超过1．15％时,延迟断裂抗力不再提高．EDS分析结果表明,钢中Mo元素在晶界发生偏聚,偏聚范围在几个纳米尺度内．通过电子能量损失谱(EELS)证明,Mo元素在原奥氏体晶界的偏聚能够提高钢的晶界结合强度．在钢中添加Mo能够显著提高钢的回火抗力和晶界结合强度,这是其具有高的延迟断裂抗力的主要原因．碳化物Mo2C对氢的捕集作用亦能够提高钢的延迟断裂抗力．Mo和V元素的二次硬化碳化物在半共格和非共格状态时,实验钢的延迟断裂抗力显著提高．     

原位合成(Ti,V)C增强铁基耐磨复合材料的研制

采用激光熔覆技术，通过调节钒含量制备多组Fe-Ti-V-C合金系统. 借助金相、SEM和XRD等分析手段对熔覆层组织和碳化物形貌进行分析. 结果表明，熔覆层中随着钒含量的提高，基体组织由F向F+M转变；颗粒状复合碳化物(Ti,V)C的数量逐渐增多，当加入钒含量超过13.3%时，初生(Ti,V)C形态由颗粒状转变为花瓣状. 此外湿砂磨粒磨损试验表明,适量钒显著改善了熔覆层的耐磨性，当钒含量为13.3%时，大量颗粒状复合碳化物(Ti,V)C均匀弥散分布在铁素体及针状马氏体基体上，使得熔覆层具有最佳的耐磨性.     

EFFECT OF SILICON ON PRODUCING DUCTILE IRON WITH COMPLEX STRUCTURE OF BAINITE AND MARTENSITE

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含钛铁基耐磨复合材料的研制

为了研制一种铁基耐磨复合材料,采用等离子熔覆技术,通过调节铬含量制备多组Fe-Cr-Ti-C合金系统.借助SEM和XRD等分析手段对熔覆层组织和碳化物形貌进行分析.结果表明,熔覆层中随着铬含量的提高,基体组织由A+F向F及M转变;碳化物M7C3及TiC等硬质相的数量逐渐增多.此外研究了铬含量对熔覆层耐磨粒磨损性能的影响规律,熔覆层的耐磨性随着铬含量的增加而提高,当铬含量达到20.1%时,大量高硬度六边形M7C3复合物结合一定量的呈开花状、球状或团聚状TiC颗粒均匀弥散分布在具有较高强韧性的板条马氏体基体中,使得熔覆层具有最佳的耐磨性.     

EFFECT OF AUSTENITIZING TEMPERATURE ON STRUCTURE AND MECHANICAL PROPERTIES OF 23NiCo ALLOY

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