预热对激光熔化沉积成形12CrNi2合金钢组织与性能的影响

使用高功率光纤激光器的快速成形系统和电磁感应加热设备,分别在未预热和预热的情况下成形12CrNi2合金钢.通过扫描电镜观察成形件微观组织、维氏硬度计测试不同部位硬度、万能材料试验机测试不同方向的拉伸性能,研究预热对激光熔化沉积12CrNi2合金钢不同方向的组织、硬度、拉伸性能的影响.结果表明:未预热条件下,单道熔池组织为板条马氏体,块状成形件熔池为回火马氏体与贝氏体混合组织,XOZ截面与YOZ截面组织没有明显的组织差别,但YOZ截面整体硬度大于XOZ截面,同时两个截面均出现了大尺寸宏观裂纹缺陷,力学性能差.在预热条件下,熔池由于温度梯度降低发生贝氏体转变,单道熔池呈现性能优异的下贝氏体组织;块状成形件熔池没有发生回火马氏体转变,主要为粒状贝氏体.截面硬度分布较未预热下更为均匀.在拉伸方向及搭接方向均呈现高强度、低塑性特征,抗拉强度可达1189 MPa,屈服强度为951 MPa,伸长率仅为2.8%,性能没有明显的各向异性.预热能够降低熔池中温度梯度,减小热应力,有效控制裂纹缺陷,促进组织均匀化,降低组织、性能的各向异性,提高合金钢成型件力学性能.     

Effects of mechanical properties on precipitation hardening stainless steel by selective laser melting,hot isostatic pressing,solid-solution and aging treatments

ABSTRACT

The selective laser melting (SLM) process has gained considerable attention from industry and academia over the recent years. Furthermore, the hot isostatic pressing (HIP) technique has been widely applied as a post-treatment to increase the relative density of the fabricated parts. The main aim of this study is to investigate the effects of porosity elimination and mechanical properties on precipitation hardening stainless steel using SLM, HIP, solid-solution and aging treatments. This study also applied various laser scanning pitches (170, 210 and 250?μm), so that a significant phase transformation occurred between the SLM, HIP, solid-solution and aging treatments. The results showed that the laser scanning pitch was 170?μm, and after HIP, solid-solution and aging treatments the materials possessed optimal mechanical properties. The highest hardness (48.8?±?0.5 HRC) and TRS (2247.0?±?157.8?MPa) could be acquired.     

高温浓硫酸中氟离子掺入对不锈钢耐蚀性能的影响

采用浸泡法和电化学测试方法结合扫描电镜和能谱仪研究了高温浓硫酸中氟离子的掺入对304、2507以及904L三种不锈钢耐蚀性能的影响.结果表明:氟离子的掺入对三种不锈钢在浓硫酸中的腐蚀具有抑制作用,综合来看,904L具有更为稳定的耐蚀性能;三种不锈钢在高温浓硫酸中由于生成了热力学不稳定的硫化镍而产生了活化转钝化现象,而掺入氟离子会和硫离子发生竞争使其排挤出电极表面,氟离子与镍离子结合形成另外一种更稳定的阻挡层使不锈钢耐蚀性提高.     

Influence of post-weld heat treatment on the microstructure and hardness of laser weld seams on hot-rolled TRIP 800 steel

The transformation induced plasticity (TRIP) steels effect occurs because of the martensitic transformation of retained austenite during plastic deformation,and it provides the steel with excellent strength and ductility.While welding remains a vital part of auto body manufacturing,the weldability of TRIP steels is problematic,and this prevents its adoption for many applications in the automotive industry.This present work studies the effects of welding and post-weld heat treatment on the microstructure of TRIP steels.It is found that the microstructures of the fusion zone and the heat affected zone (HAZ) are changed after high-temperature heat treatment.Hardness tests revealed that fusion zone hardness decreased with increasing of temperatures in the post-weld heat treatment on the laser weld seam.The rolling performance of the welding seam and the seam of post-weld heat treatment were also studied.     

Effects of CeO_2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers

The effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers were investigated. The results showed that carbides presented in cladding layers were TiVC2 and VC. A small quantity of CeC appeared with 2.0 wt.% CeO2 addition. The amount of lamellar pearlite increased while the amount of residual austenite decreased with increasing CeO2 addition. The corrosion resistance of cladding layers increased firstly and then decreased with the addition of CeO2 increasing. The EIS spectrum of the cladding layer without CeO2 was composed of an inductive arc at low frequency and a capacitive arc at high frequency. The cladding layer with 0.5 wt.% CeO2 addition showed the best corrosion resistance, and then the inductive arc at low frequency transformed into a capacitive arc.     

高强度海工钢中腐蚀活性夹杂物与耐海水腐蚀性能研究

利用金相显微镜(OM)和扫描电子显微镜(SEM)观察和分析不同厚度(12和35.5 mm)的EH36钢板中腐蚀活性夹杂物的形貌和尺寸分布;使用X射线能谱仪(EDS)分析腐蚀活性夹杂物的成分;采用电化学腐蚀和室内模拟海水加速腐蚀实验分析EH36钢板的耐腐蚀性能.结果表明:活性夹杂物主要成分为Al、Mg复合氧化物,组成主要...     

硼微合金化对6Mo超级奥氏体不锈钢微观组织及耐蚀性影响

综述了6Mo超级奥氏体不锈钢凝固、热加工和热处理阶段的微观组织演化规律,并分析了合金元素对Mo偏析和σ相析出及耐蚀性能的影响规律.结合作者前期工作,重点分析了微合金化元素硼对其凝固阶段Mo偏析、热加工和热处理阶段σ相析出以及耐蚀性能的影响.硼抑制热加工过程中σ相的析出,减小析出相数量和尺寸,有利于热塑性提高;同时还可促...     

Influence of adding various rare earths on microstructures and corrosion resistance of chromizing coatings prepared via pack cementation on P110 steel

In order to improve the corrosion resistance and increase the service lifetime of P110 steel during operation,four chromizing coatings were formed onto its surface with/without addition of rare earths via pack cementation process.The surface morphologies and microstructures of the chromizing coatings were observed using scanning electron microscopy(SEM),and the phase constitutions were investigated by X-ray diffraction(XRD).Electrochemical corrosion behavior of the chromizing coatings in simulated oilfield ...     

pH值对高温高压水中304L不锈钢应力腐蚀开裂的影响

在高温高压水环境中,采用慢应变速率拉伸试验方法,研究了不同pH值对304L不锈钢应力腐蚀开裂行为的影响规律,并通过扫描电镜对试样断口形貌进行观察与分析.结果表明:在300℃时,304L不锈钢在弱酸性和弱碱性溶液中的应力腐蚀开裂敏感性较大,且酸性越强,敏感性越大.在中性溶液中,304L不锈钢的强度和塑性损失较小,应力腐蚀敏感性较小,断口分析与之吻合.     

16Mn(HIC)钢硫化物应力腐蚀开裂实验研究

采用恒应变和慢应变速率拉伸实验的方法,研究了16Mn(HIC)和16Mn钢母材、焊缝在H₂S环境中应力腐蚀开裂.结果表明两种材料在酸性H₂S介质中均发生穿晶型硫化物应力腐蚀开裂(SSCC);与16Mn钢相比,16Mn(HIC)钢有更好的抗SSCC性能,钢中的C,Mn,P和S的含量降低有利于提高钢的抗SSCC性能.焊缝及热影响区在焊接过程中,产生的粗大魏氏组织、偏析、缩孔和夹杂等缺陷,降低了焊缝的抗SSCC能力.但是,通过焊后热处理可以适当提高焊缝的抗SSCC能力.