金属粉床增材制造奥氏体不锈钢的研究进展

摘要：金属增材制造技术成形奥氏体不锈钢易出现与传统制备方法完全不同的非平衡亚稳微观组织,表现出独特的性能,其中激光增材制造的316L不锈钢,兼具高屈服强度、良好的伸长率以及优异的耐腐蚀性能。系统综述了近年来国内外激光增材制造316L不锈钢的研究进展,针对其高冷却速率、微熔池冶金、强非平衡凝固和复杂热履历成形条件,阐述其微观组织结构的形成机制和调控方法,以及对力学性能和腐蚀行为的影响规律,重点分析了激光增材制造316L奥氏体不锈钢的强韧化机制,最后展望增材制造奥氏体不锈钢的未来研究方向。     

选区激光熔化工艺参数对气雾化 316L不锈钢粉末成形制品性能的影响

本研究系统考察了激光功率和扫描速度对316L不锈钢粉末选区激光熔化工艺成形熔道、制品微观组织及力学性能的影响,并分析了各类缺陷的形成原因。研究结果表明:在低激光功率和高扫描速度条件下,熔道中出现了大量球状颗粒,这些颗粒之间的空隙恶化了下一层粉末的熔化条件,这正是成形制品中熔道分布混乱以及孔洞、裂纹产生的根本原因,进而导致成形制品力学性能降低;在高激光功率和低扫描速度条件下,熔池快速升温/冷却的热应力作用增强,使得成形制品的熔道交界处也存在孔洞和裂纹等缺陷。在本研究实验条件下,激光功率为350 W,扫描速度为1750 mm/s时,SLM成形制品的力学性能最为优异,其中抗拉强度为731 MPa、屈服强度为638 MPa、断后伸长率为40.0%,致密度为96.27%。     

445J2超纯铁素体不锈钢和316L超低碳奥氏体不锈钢在溴化锂溶液的点蚀分析

445J2铁素体不锈钢由于高的导热率、低的热膨胀系数以及良好的耐蚀性能使得其作为溴冷机中一些部件的良好候选材料,本文采用电化学测试方法对比研究了445J2超纯铁素体不锈钢(/%:0.01C,22.5Cr, 1.9Mo, 0.27Nb, 0.20Ti, 0.09Al, 0.36Cu, 0.015P,0.001S,0.015N)和316L奥氏体不锈钢(/%:0.002C,16.8Cr, 10.19Ni, 2.02Mo, 0.025P,0.0008S)在20～60℃0.1～1M的溴化锂溶液中的点蚀行为,并采用扫描电镜(SEM)和能谱分析仪(EDS)对电化学结果进行表征。结果表明,随着LiBr温度和浓度的升高,两种钢腐蚀电流密度增大,点蚀电位降低,耐点蚀性变差;氧化物和硫化物夹杂会引起两种钢的点蚀;高含量的Cr以及Mo、Ti、Nb、Al等合金元素使445J2钢具有优异的耐点蚀性能。     

高分子复合波纹膨胀节在高炉煤气系统上的研发与应用

介绍了高分子复合波纹膨胀节的耐煤气腐蚀机理、优异性能,从根本上解决了目前316L、800镍基合金、超级奥氏体不锈钢等金属补偿器无法解决的晶界腐蚀问题。     

Heterogeneity and Solidification Pathways in Additively Manufactured 316L Stainless Steels

Metallurgical and Materials Transactions A - A unique microstructural feature often referred to as “fish-scale” has been reported in 316L austenitic stainless steel parts made by laser...     

Towards the Optimization of Post-Laser Powder Bed Fusion Stress-Relieve Treatments of Stainless Steel 316L

The use of post-processing heat treatments is often considered a necessary approach to relax high-magnitude residual stresses (RS) formed during the layerwise additive manufacturing laser powder bed fusion (LPBF). In this work, three heat treatment strategies using temperatures of 450 °C, 800 °C, and 900 °C are applied to austenitic stainless steel 316L samples manufactured by LPBF. These temperatures encompass the suggested lower and upper bounds of heat treatment temperatures of conventionally processed 316L. The relaxation of the RS is characterized by neutron diffraction (ND), and the associated changes of the microstructure are analyzed using electron backscattered diffraction (EBSD) and scanning electron microscopy (SEM). The lower bound heat treatment variant of 450 °C for 4 hours exhibited high tensile and compressive RS. When applying subsequent heat treatments, we show that stress gradients are still observed after applying 800 °C for 1 hour but almost completely vanish when applying 900 °C for 1 hour. The observed near complete relaxation of the RS appears to be closely related to the evolution of the characteristic subgrain solidification cellular microstructure.

     

High performance ferritic stainless steel B445R for architectural applications

Traditionally,austenitic stainless steels 304 and 316 have been employed in coastal regions as roofing materials unfortunately,they are expensive and not fully resistant to pitting corrosion under severe coastal corrosive environment.A ferritic stainless steel B445R was developed.Compared with austenitic 316L,B445R is①less costly;②uperior corrosion resistant with minor maintenance for long-term service;③insusceptible to thermal distortion in the welding seam. B445R sheet shows a higher yield strength and lower tensile strength,lower elongation and lower work-hardening than austenitic 316L.It can be easily fabricated and deformed just like plain carbon steel.After bending 180o,there is no occurrence of "cracking" or noticeable "orange peel".The formability of the welding seam is also satisfactory.The pitting potential of B445R is 650 mV,larger than that of 304 and 316L,as shown in Fig.1. The corrosion rate of B445R submerged in 6%FeCl,solution is 0.3 -0.56 g/(m² ? h^-1),much lower than that of 316L,as shown in Fig.2.The superior pitting corrosion resistance of B445R can be ascribed to synergetic effect of higher Cr and Mo. Dull-finished B445R sheets have been employed as the roofing materials for Guangzhou Asian Games Arena,as shown in Fig.3.About 380 t of 1.0 mm B445R with dull finish was used for roofing panels.About 100 t of 0.8 mm B445R with hairline or fluororesin paint finish was used for side wall panels.The composite roof build-up （from up to bottom） includes:①shingles of ferritic stainless steel B445R;②Kalzip-type standing seam of austenitic 304;③water-proof DFM;④structural steel;⑤75 mm thick insulation;⑥secondary purlin of 150 mm×100 mm×4.5 mm of galvanizied Q235;⑦0.8 mm thick profile deck of galvanizied Q235;⑧acoustic insulation.The roofing shingles or panels with the same width but different length were formed by bending four sides and fixed to a "L" shape reinforcing frames of stainless steel by fasteners.The "L" frames was connected to ribs of the standing seam by a clamping fixture made of aluminum.     

Microstructure of 316L stainless steel components produced by direct laser deposition

The prospects for direct laser deposition in the manufacture of 316L austenitic stainless steel parts are assessed. The influence of the power of the laser beam and the state of the initial material on the structure and properties of the product is considered.     

Development of ferritic stainless steel B445R with superior corrosion resistance for architectural applications

The dull-finish ferritic stainless steel(FSS) sheet B445R for architectural roofing has been developed by Baosteel.This steel product exhibits excellent corrosion resistance superior to that of SUS 316L with a lower cost.It can be easily formed into roofing panels by ordinary processes.Moreover,the thermal strain of it is less than SUS 316L because of its lower thermal expansion coefficient,and its reflectivity is lower due to the dull-finish treatment.All of these features make it capable of being used as architectural roofing materials in coastal regions.     

Effect of Additive Cu-10Sn on Sintering Behavior and Wear Resistance of 316L Stainless Steel

 Austenitic 316L stainless steel has good corrosion resistance; however, the relative softness often limits its application. Severe adhesive wear often occurs between the 316L stainless steel and the metal counterpart. Cu-10Sn alloy is often used to improve the wear resistance of powder metallurgy 316L stainless steel. The influence of Cu-10Sn on sintering behavior and wear resistance of powder metallurgy 316L stainless steel was investigated. The parameters investigated included sintering temperature and volume percent of Cu-10Sn. A maximum relative density of 97% was achieved with 25% (in volume percent) Cu-10Sn content at a sintering temperature of 1300 ℃ for 60 min. The irregular and sharp angles of 316L stainless steel particles become round, and the pores are removed completely as a result of large amount of liquid phase formed during sintering. The minimum friction mass loss was achieved with 25% Cu-10Sn content.     

增材制造17-4PH马氏体不锈钢研究进展

17-4PH马氏体不锈钢具有高强高韧以及耐腐蚀等优异性能,在航空航天、核能和民用工业等领域得到广泛的应用。增材制造技术通过离散堆积的制备方法,能够实现复杂异形零部件的成形,满足装备迭代的需求。综述了国内外增材制造17-4PH的研究成果,针对增材制造微小熔池、快速熔凝、复杂热历史冶金特点,介绍影响增材制造17-4PH试样致密度的因素,阐述其相构成、微观组织和力学性能,简述后处理对17-4PH力学性能的影响规律,最后对增材制造17-4PH的发展进行展望。     

建筑用高耐蚀性铁素体不锈钢B445R的研制

宝钢研制出了建筑屋顶装饰用铁素体不锈钢B445R毛面产品。该产品的耐蚀性比奥氏体不锈钢SUS316L更优越,成本也比SUS316L低,采用常规的成形方法就可以将其加工成屋顶面板。此外,由于该产品的热膨胀系数比SUS316L小,故其热变形也比SUS316L小,同时由于进行了毛化处理,其表面具有较低的光反射能力。所有这些优点使其有能力成为沿海地区建筑物的屋顶装饰材料。     

氮对316L型不锈钢等离子弧焊接性能的影响

氮作为一种强奥氏体化元素,在不降低韧性的前提下可以提高材料强度和抗腐蚀性能。为了研究氮含量对316L型不锈钢焊接性能的影响,采用两种不同氮含量的316L型不锈钢进行不填丝穿孔等离子弧焊接。通过力学、抗晶间腐蚀等性能的对比,结合金相组织观察,可以看出奥氏体不锈钢中氮元素含量的增加能够提高焊接接头的抗拉强度,但却促进了热影响区晶粒的粗化,导致热影响区的低温冲击性能降低。     

Powder metallurgical production of 316L stainless steel/niobium composites for Proton Exchange membrane electrolysis cells

In this study, a composite made of a porous stainless steel (SS) 316L substrate coated with Nb was investigated as a novel porous transport layer (PTL) for proton exchange membrane electrolysis cells (PEMECs). The fabrication of such SS316L/Nb composites using scalable and automatable powder metallurgical techniques as tape casting, screen-printing and field assisted sintering technology/spark plasma sintering (FAST/SPS) was described. Sintering behaviour and the interdiffusion at the SS316L/Nb interface were investigated. Powder metallurgical techniques such as screen-printing are the preferred method to achieve a porous Nb coating, while FAST/SPS is the preferred method for a better control of the SS316L/Nb interface by lowered interdiffusion. First electrochemical performance tests with SS316L/Nb composites demonstrate they have potential to replace the state-of-the-art titanium-based PTLs. The use of SS316L is expected to decrease manufacturing costs of PTLs, while the addition of niobium layer, due to its excellent corrosion resistance in acid environment, aims to improve PEMECs lifetime and performance.     

热处理对SLM-316L不锈钢组织结构及钝化行为的影响机制

对SLM-316L不锈钢在900℃下进行不同时间的热处理,结合热处理后SLM-316L不锈钢的组织结构和腐蚀行为研究,揭示了SLM-316L不锈钢在900℃热处理过程中组织结构的演变规律以及其对钝化行为的作用机制.研究结果表明,900℃热处理时,在组织结构方面,SLM-316L不锈钢晶粒的基本形状和尺寸没有明显变化,但是随着保温时间延长,SLM-316L不锈钢中的位错和亚晶界逐渐消失,同时伴有MnS颗粒物沿晶界析出;在耐蚀性能方面,热处理对SLM-316L不锈钢的耐蚀性能产生重要影响,在含有NaCl的缓冲溶液中,SLM-316L不锈钢的点蚀电位随着保温时间延长逐渐降低,同时电化学阻抗逐渐减小;此外,在钝化膜性质方面,不同热处理时间试样上形成的钝化膜有明显差异,随着保温时间延长,SLM-316L不锈钢钝化膜的厚度逐渐减小,载流子的密度以及扩散系数变大.最后,通过构建不锈钢钝化膜能带结构和空间电荷层的理论模型,讨论了热处理对SLM-316L不锈钢钝化行为的影响机制.     

奥氏体不锈钢中σ相析出及其对性能影响的研究进展简

 针对用于ITER(International Thermonuclear Experimental Reactor)的316L(N)型奥氏体不锈钢，研究分析了其中形成的σ相的特征、相形成过程、检测方法以及对性能的影响，以加深基础研究工作者和工程技术人员对σ相的了解，促进316L(N)生产工艺的完善和产品质量的进一步提高。结合相关研究的最新进展，展望了今后的研究及发展趋势。     

Effect of heating mode and electrochemical response on austenitic and ferritic stainless steels

Abstract

Powder metallurgical (P/M) processing has the main advantage of making near net shape products. Nowadays, in automobile industries, stainless steels have become the most promising material owing to their good corrosion resistance. In the current study, 316L and 434L stainless steel powders were sintered using microwave and conventional methods through powder metallurgy route. The effects of sintering modes on the microstructure, mechanical properties and corrosion responses of 316L and 434L stainless steel composites are investigated in detail. The results showed that the sample prepared through microwave sintering route exhibited significantly superior densification, higher hardness and better corrosion resistance as compared to the conventionally processed counterpart. On the whole, 316L composites showed better corrosion resistance than 434L stainless steels.     

奥氏体不锈钢粉末压坯的液相烧结

综述了添加元素对奥氏体不锈钢粉末压坯液相烧结行为及材料性能的影响。加铜可以改善材料的耐腐蚀性并提高其力学性能；加硅可以提高材料的力学性能，特别是韧性；加铝影响材料的致密化行为。     

TMCP工艺轧制桥梁用不锈钢复合板的组织与性能

为了获得桥梁用不锈钢复合板良好的综合性能,采用控轧控冷(thermal mechanical control process,简称TMCP)工艺轧制了桥梁用不锈钢复合板316L+Q370qD,利用金相、扫描、拉伸、冲击、弯曲、剪切和晶间腐蚀等手段研究了该复合板的组织与性能。结果表明,316L+Q370qD桥梁用不锈钢复合板的界面实现了完全冶金结合,未发现孔洞、裂纹等缺陷以及大颗粒的析出物及氧化物夹杂等;复合板的屈服强度为421~446MPa,伸长率为24.0%~28.0%,-20℃纵向冲击吸收能量平均值为200J,180°内、外弯曲合格,平均剪切强度为412 MPa,复合板的各项力学性能均满足GB/T 8165—2008《不锈钢复合钢板和钢带》标准要求。按照GB/T 4334—2008方法 E进行晶间腐蚀试验,复层不锈钢316L未出现晶间腐蚀现象,具有良好的耐晶间腐蚀性能。     

Effect of sintering temperature, heating mode and graphite addition on the corrosion response of austenitic and ferritic stainless steels

In recent years, sintered stainless steel with carbon addition has been proposed for potential use as exhaust flanges in automotive applications. The net-shaping requirements for such applications necessitate the use of powder metallurgical (P/M) processing route. However, due to the presence of porosity, most sintered steels have poor corrosion resistance. The present study compares the effect of sintering temperature, heating mode and graphite addition (up to 1.5%) on the densification and electrochemical response of both ferritic (434L) and austenitic (316L) stainless steels. The compacts were sintered in both conventional (radiatively heated) as well as microwave furnace. As compared to conventional sintering, samples consolidated in microwaves have higher densification (particularly at 1200°C) and exhibit better corrosion properties.