高硼不锈钢复合板力学性能研究

采用包覆浇铸+热成形方法制备出含硼量在2%～2.5%的高硼不锈钢复合板。三点弯曲实验表明,固溶处理后中间层的含硼不锈钢其拉伸和压缩变形量分别达到5.6%和6.0%,固溶后的含硼不锈钢复合板表现出的塑性已接近ASTM A887标准中的304BN7(B级)。采用这种复合材料的结构设计,可使含硼不锈钢复合板表现出比单一材料弯曲时更好的塑性。复合板发生断裂时,覆层和中间层的基体断口均显示出典型的韧窝形貌。中间层中硼化物和基体之间的断口为解理断口,使其塑性降低。     

硼对高铬铸铁铸渗层组织和性能的影响

本工作利用自熔铸渗技术在ZG45钢表面复合不同硼含量的高铬铸铁铸渗层,研究了硼对高铬铸铁铸渗层组织和性能的影响.利用相图计算软件Thermo-Calc计算分析了不同硼含量下铸渗层的凝固过程,并采用SEM-EDS、XRD和显微硬度仪对不同成分铸渗层的微观组织和硬度进行分析.结果表明:铸渗层与ZG45钢基体达到冶金结合,在结合界面处未观察到微孔洞、微裂纹等缺陷,获得了厚度为10～12 mm的铸渗层.不含硼的铸渗层组织由α-Fe和α-Fe+M7 C3共晶组织组成.加入微量的硼元素后,铸渗层组织主要由α-Fe与α-Fe+M7 C3+M2 B共晶组织组成,与相图计算结果基本吻合.随着硼含量的增加,共晶组织逐渐细化,M7 C3碳化物含量减少,M2 B型硼化物增多,铸渗层硬度逐渐增加.当硼含量为0.72％(质量分数)时,铸渗层硬度最高达到1190HV.对铸态试样进行淬火+低温回火热处理后,铸渗层共晶硼化物与碳化物发生聚集长大,同时在铸渗层基体中伴有二次相的析出,试样铸渗层的洛氏硬度均有提升.热处理试样冲击磨损实验表明,铸渗层磨损表面主要以切削犁沟、疲劳剥层和剥落坑为主,并有少量微小的凿坑.硼含量为0.72％(质量分数)时,试样的抗冲击磨损性能最佳.     

高硼中碳合金工具钢的铸态组织

针对普通高速钢含有大量贵重合金元素的缺陷,设计了一种用廉价的硼元素部分取代普通高速钢中价格昂贵的铬、钨、钼、钒等合金元素的新型耐磨材料。借助光学显微镜(OM)、X射线衍射(XRD)、扫描电镜(SEM)和能谱仪(EDS)等手段对高硼中碳合金工具钢的铸态组织进行了分析。结果表明:高硼中碳合金工具钢铸态组织由马氏体、少量残留奥氏体及Fe2B,Fe3(B,C),Fe23(B,C)6,Cr7(B,C)3和(W,Mo)2(B,C)等共晶硼碳化合物或硼化物组成。其基体和共晶硬质相的显微硬度分别为540～620HV和1180～1520HV,铸态宏观硬度达到55HRC。     

硼含量对IC10高温合金凝固行为的影响

采用差示扫描量热(DSC)、等温淬火和显微组织分析方法对比分析含硼量为0.005%(质量分数,下同)和0.03%的IC10合金显微组织及组成相的形成过程,研究不同硼含量合金中初生相的析出温度及析出顺序。结果表明:DSC的冷却曲线上可显示出γ、MC碳化物、(γ+γ′)共晶以及次生γ′的析出峰,但微量相M3B2硼化物和Ni5Hf相未能显示。等温淬火法可以确定所有相的析出温度。不同含硼量合金的相组成相同,按形成先后顺序六种相分别为γ、MC、(γ+γ′)共晶、次生γ′、M3B2和Ni5Hf。IC10合金含硼量的增加,显著提高了M3B2和(γ+γ′)共晶的含量(体积分数),使合金液相线和固相线温度降低,同时延缓了MC碳化物和(γ+γ′)共晶的形成。     

铸态及快淬态La2Mg(Ni0.85Co0.15)9Bx(x=O～O.2)贮氢合金的微观结构与电化学容量

用铸造及快淬工艺制备了La-Mg-Ni系(PuNi3型)贮氢合金La2Mg(Ni0.85Co0.15)9Bx(x=0,0.05,0.1,0.15,0.2),分析测试了铸态及快淬态合金的微观结构与电化学容量,研究了硼及快淬工艺对合金微观结构及电化学容量的影响.结果表明,铸态合金具有多相结构,包括(La,Mg)Ni3相(PuNi3型)、LaNi5相,一定量的LaNi2相和微量的Ni2B相,经快淬处理后Ni2B相消失.硼的加入对铸态及快淬态合金的容量产生不同的影响,铸态合金的容量随硼含量的增加而单调下降,而快淬态合金的容量随硼含量的增加有一极大值.快淬处理对含硼及不含硼合金的容量也有不同的影响,随淬速的增加,不含硼合金的容量单调下降,而含硼合金的容量可以获得一个极大值.     

铸态及快淬态La_2Mg(Ni_(0.85)Co_(0.15))_9B_x(x=0~0.2)贮氢合金的微观结构与电化学容量(英文)

用铸造及快淬工艺制备了La-Mg-Ni系(PuNi3型)贮氢合金La2Mg(Ni0.85Co0.15)9Bx(x=0,0.05,0.1,0.15,0.2),分析测试了铸态及快淬态合金的微观结构与电化学容量,研究了硼及快淬工艺对合金微观结构及电化学容量的影响。结果表明,铸态合金具有多相结构,包括(La,Mg)Ni3相(PuNi3型)、LaNi5相,一定量的LaNi2相和微量的Ni2B相,经快淬处理后Ni2B相消失。硼的加入对铸态及快淬态合金的容量产生不同的影响,铸态合金的容量随硼含量的增加而单调下降,而快淬态合金的容量随硼含量的增加有一极大值。快淬处理对含硼及不含硼合金的容量也有不同的影响,随淬速的增加,不含硼合金的容量单调下降,而含硼合金的容量可以获得一个极大值。     

铸态及快淬态La2Mg（Ni.85Co0.15）9Bx（x=0～0.2）贮氢合金的微观结构与电化学容量

用铸造及快淬工艺制备了La-Mg-Ni系（PuNi3型）贮氢合金La2Mg（Ni.85Co0.15）9Bx（x=0,0．05，0．1，0．15，0．2），分析测试了铸态及快淬态合金的微观结构与电化学容量，研究了硼及快淬工艺对合金微观结构及电化学容量的影响。结果表明，铸态合金具有多相结构，包括（La，Mg）Ni3相（PuNi3型）、LaNi5相，一定量的LaNi2相和微量的Ni2B相，经快淬处理后Ni2B相消失。硼的加入对铸态及快淬态舍金的容量产生不同的影响，铸态合金的容量随硼含量的增加而单调下降，而快淬态含金的容量随硼含量的增加有一极大值。快淬处理对含硼及不含硼合金的容量也有不同的影响，随淬速的增加，不含硼合金的容量单调下降，而含硼合金的容量可以获得一个极大值。     

梯度结构半固态9 Cr18不锈钢的制备与显微组织演变

基于Gleeble3500热模拟试验机设计了半固态触变锻造成形装置,通过触变锻造工艺制备了9Cr18不锈钢制件,研究其显微组织结构和演变特征.研究结果表明,半固态触变成形装置能够实现9Cr18半固态坯料成形.在触变锻造成形过程中,固相骨架破碎后,半固态坯料表现出触变特性,载荷随着变形的进行而下降.9Cr18触变制件变形区呈现梯度结构的显微组织特征.触变制件边部存在明显的液/固分界层.分界层外侧为液相凝固形成的共晶组织;分界层内侧主要为固相颗粒.9Cr18触变制件具有独特的组织演变规律,其内部主要为具有良好塑性变形能力的奥氏体组织,表层存在大量的M7 C3共晶碳化物,二者共同保证了9Cr18不锈钢触变制件具有"外硬内韧"的特征.     

L415/IN825复合板焊接接头渗硼处理工艺及渗层的组织与性能

目前对双金属复合板焊接接头的渗硼处理鲜有研究报道。为了提高双金属复合板焊接接头的耐蚀和耐磨性能,对其表面进行渗硼处理。采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)及显微硬度计分别对L415/IN825复合板复层焊接接头渗层的微观组织、物相组成及显微硬度进行了分析,并研究了复合板焊接接头及其渗层电化学腐蚀性能。结果表明:复合板焊接接头复层渗层分为硼化物层(Ni_2B、Cr_5B_3、Cr_2B和CrB)和硅化物层(Ni_2Si、Cr_3Ni_2Si和Cr_(13)Ni_5Si_2),全渗层的厚度随着加热温度和保温时间的增加而增加;不同区域渗层表面的显微硬度值均高于基体;复合板焊接接头基体耐蚀性能优于焊接接头表面渗层。     

特超级双相不锈钢CD3MWN的组织和性能研究

研究了不同固溶处理温度对特超级双相不锈钢CD3MWN的组织及性能的影响。结果表明,在铸态下其组织中出现了大量的析出相;在1 060℃固溶处理时,σ相不能完全消除;在1 080～1 120℃固溶处理时,铁素体含量可以达到55%～57%;当固溶温度从1 060℃提高到1 100℃时,拉伸强度和硬度逐渐降低,冲击性能逐渐增强;当固溶温度从1 100℃提高到1 140℃时,拉伸强度和硬度逐渐增加,冲击性能逐渐降低;CD3MWN钢的耐点蚀性能和耐缝隙腐蚀性能优于CD3MN钢和CN7MS钢的。     

Hardfacing of stainless steel with laser melted colmonoy

Stainless steel substrates were hardfaced with laser melted Colmonoy applying a continuous wire injection technique using a CO₂ laser. The microstructures of single pass laser clad deposits were examined and related to workpiece traverse velocity at constant laser output. Particular attention was paid to the effect of dilution of the cladding alloy due to convectional mixing with the partially melted substrate material. The solidification microstructure of the rapidly cooled cladded layer consisted predominantly of nickel rich cellular dendrites and interdendritic lamellar eutectic borides.     

Origin of flakes on stainless steel heater

The corrosion resistance of AISI 321 stainless steel depends on the formation of thin and compact Cr₂O₃ oxide layer that protects the steel surface. But sometimes anomalies appear, that enable formation of the protective layer and the steel becomes sensitive to oxidation at elevated temperatures. In such a case, the oxide layer is not compact enough and the oxide fall off the surface. Presented are investigations of flakes on the surface of stainless steel heaters for household application. The flakes appeared during the first short time heating test of the heater. Analyses revealed that the flakes on the heaters originated from the hot rolling process. The rolled in hot cracks enabled the formation of the flakes on the surface of the heater.     

Microstructural control by secondary processing of strip cast low carbon steel

Abstract

The secondary processing of low carbon steel strip produced by twin roll casting was investigated to examine its effect on microstructural development and mechanical properties. The as cast microstructure is predominantly acicular ferrite with regions of bainitepearlite and polygonal ferrite. Deformation at temperatures below Ar1 produces a heterogeneous microstructure with regions of moderately deformed acicular ferrite adjacent to highly deformed regions containing shear bands. Cold rolled and warm rolled steels show similar behaviour to conventional hot band in that dynamic recovery during warm rolling results in sluggish recrystallisation and produces a coarse final grain size. However, the initial as cast microstructure recrystallises at a slower rate than conventional hot band and produces a weaker recrystallisation texture. This can be attributed to the heterogeneous microstructure of the as cast strip such that, after rolling, nucleation occurs within shear bands and more ill defined sites, which results in nucleation of randomly oriented grains thereby producing a weak final texture. It was found that austenitising the as cast strip followed by rolling in the vicinity of Ar3 produces a uniform distribution of equiaxed, ultrafine ferrite UFF grains throughout the thickness of the strip. The production of UFF by twin roll casting and subsequent rolling represents a simple processing route for the production of fine grained low carbon sheet steel products.     

Failure analysis of a martensitic stainless steel (CA-15M) roll manufactured by centrifugal casting. Part I: Material and fractographic characterization

The failure analysis of a martensitic stainless steel (CA-15M) roll manufactured by centrifugal casting and used in cast glass rolling was carried out by means of traditional characterization techniques (optical metallography, SEM, EDX microanalysis, tensile testing and XRD). The roll was in the as-cast condition and its microstructure featured large proportion of δ ferrite (between 20% and 27%) in a martensitic (α′) matrix, with the δ/α′ interfaces presenting an intergranular network of M₂₃C₆ carbides. The crack propagation began in the internal surface of the roll, with δ/α′ intergranular and transgranular cleavage in the “equiaxed region” of the casting, progressing to δ/α′ intergranular ductile fracture in the “columnar” and “chilled regions”. Tensile thermal stresses in the internal surface of the roll associated with microstructural embrittlement (network of interfacial carbide and microporosities) are thought to be the main causes for the premature failure of the roll. Finally, materials selection was performed to replace the CA-15M stainless steel with another class of stainless steel for centrifugal casting.     

Solidification structure in a cast B-bearing stainless steel

Solidification microstructure of a cast stainless steel containing 1.5–2.5 wt.%B has been examined by means of the optical microscopy (OM), the scanning electron microscopy (SEM), the electron probe microanalyzer (EPMA), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and Vickers microhardness. The as-cast microstructure consists of the M₂(B,C) borocarbide and the austenite. The borocarbide is continuously distributed over the austenite. There are some broken-networks in the local location of borocarbide. Moreover, the distribution of alloy elements is not homogeneous in the cast B-bearing stainless steel. Boron element is mainly distributed over the borocarbide, carbon element is mainly distributed over the matrix. Chromium element is mainly distributed over the borocarbide, and there are also some chromium elements in the matrix. Nickel element is mainly distributed over the matrix and silicon is insoluble in the borocarbide.     

Design of wear resistant boron-modified supermartensitic stainless steel by spray forming process

In this paper the chemical composition of the supermartensitic stainless (SM) was modified with the addition of small boron contents (0.3, 0.5 and 0.7 wt.%) and processed by spray forming aiming the development of functionalized stainless steel with higher wear resistance. The addition of boron to the SM leads to the formation of continuous network of M₂B type borides uniformly distributed in the refined microstructure promoted by the spray forming process. The wear resistance was evaluated by two different methodologies: (1) the standardized dry sand/rubber wheel test (ASTM G65); and (2) a plate-on-cylinder (POC) wear test which was designed to simulate in laboratorial scale the tribosystems found in wear of risers and casings. It was shown that the wear mechanisms that take place in both tests are quite different, but in all cases increasing the boron content is always accompanied by an increase in the wear resistance. Electrochemical analyses were performed to evaluate the corrosion resistance of the designed alloys. It could be seen that corrosion properties similar to the commercial SM can be achieved in the SM modified with 0.7 wt.% of boron if an over content of chromium is added to the chemical composition.     

Hot cracking susceptibility of boron modified AISI 304 austenitic stainless steel welds

Abstract

The hot cracking susceptibility of welds made on AISI 304 stainless steel modified with from 0·2 to 1·0 wt-%B has been investigated. Varestraint tests showed that the hot cracking susceptibility is high for boron additions of about 0·2%, but is decreased when the boron content is increased to ≥0·5%. Steels containing about 0·2%B were found to have a wide solidification temperature range and their high temperature ductility was low compared with boron free AISI 304 steel and the other boron modified steels. Ferrite precipitation was inhibited in the 0·2%B steels and the formation of low melting point grain boundary films was thereby promoted. Increasing the boron content to ≥0·6% reduces the coefficient of thermal expansion and narrows the solidification temperature range. In addition, crack refilling was observed, resulting in improved hot ductility and high resistance to hot cracking. It is concluded that in structures where weld restraint forces are not high, hot cracking is not likely to occur if boron additions of >0·6% are made to AISI 304 stainless steel. In T-type and Fisco weld cracking tests, in which the weld restraint forces are close to those experienced by actual structural welds, the boron modified stainless steels show a low hot cracking susceptibility which is not significantly different from that of boron free AISI 304 steel.

MST/1548     

水导轴承等离子堆焊Ni60合金组织及其耐腐蚀性能

采用等离子堆焊技术在Z2CN18-10核电用不锈钢表面堆焊Ni60合金,并研究Ni60合金堆焊层的组织结构、硬度和耐蚀性能。结果表明:堆焊层组织主要由γ-Ni、碳化物、硼化物以及γ-Ni和硼化物的共晶组成,堆焊层的底层、中间层和顶层位置各相体积分数不同,中间层菊花状组织最多。Ni60堆焊层硬度约为500HV,明显高于Z2CN18-10不锈钢基体,菊花状共晶组织有助于提高堆焊层硬度。Ni60在硼酸中的钝化能力明显高于海水,且与Z2CN18-10不锈钢的自腐蚀电位差较小,不易发生电偶腐蚀。在模拟海水中堆焊层中间层耐腐蚀性能优于堆焊层的底部和顶部,与基体的自腐蚀电位差较大,容易出现电偶腐蚀。     

轧制工艺对316L不锈钢组织和耐蚀性能的影响

为探索改善不锈钢耐腐蚀性能的途径,对316L不锈钢施加相同变形量的同步轧制和异步轧制,利用X射线衍射、透射电镜观察、电化学测量和扫描电镜表面观察研究了轧制工艺对钢的显微组织和腐蚀性能的影响.结果表明,经过异步轧制后显微组织中出现大量孪晶界,优化了晶界结构,在酸性介质中的晶间腐蚀敏感性明显减轻;而经过同步轧制后,样品呈现出高位错密度的显微组织,在酸性介质中的耐腐蚀性能降低.异步轧制后耐蚀性能得到改善是由于大量孪晶界的形成优化了晶界结构.     

Structure and properties of strengthening layer on Hardox 450 steel

The microstructure and microhardness distribution in the surface of low-carbon Hardox 450 steel coated with alloyed powder wires of different chemical compositions are studied. It is shown that the microhardness of 6–8?mm-thick surfaced layer exceeds that of base metal by more than two times. The increased mechanical properties of surfaced layer are caused by the submicro and nanoscale dispersed martensite, containing the niobium carbides Nb₂C, NbC and iron borides Fe₂B. In the bulk plates, a dislocation substructure of the net-like type with scalar dislocation density of 10¹¹?cm^?2 is observed. The layer surfaced with the wire containing B possesses highest hardness. The possible mechanisms and temperature regimes of niobium and boron carbides in surfacing are discussed.