铬对交流电场增强粉末法渗硼层组织和性能的影响

在低硼势粉末法渗硼剂中加入适量的铬粉,于750 ℃对45钢进行交流电场增强渗硼,研究Cr对电场增强粉末法渗硼的影响。采用光学显微镜、X射线衍射仪和显微硬度计对渗层组织、厚度、相与显微硬度进行观察和分析。试验结果表明:采用含3%硼铁的渗剂,渗硼层为典型的锯齿状硼化物,主要为Fe₂B相;当渗剂中加入微量铬粉时,最高硬度基本不变,渗层厚度增加,且在铬粉含量为0.2%时达最厚,较不加铬粉的提高约80%,之后降低;当铬粉含量高于3%后,渗层的最高硬度降低;当加入的铬粉≥5%时,渗层表层还出现多种含铬相。     

65Mn钢渗硼层的微观组织、硬度及生长动力学

采用固体渗硼工艺对65Mn钢进行渗硼处理,并借助光学显微镜、X射线衍射仪、电子探针及维氏硬度计等手段系统研究了渗硼温度(800~1000 ℃)和渗硼保温时间(2~8 h)对65Mn钢渗硼层厚度、微观组织和硬度的影响规律以及渗硼层的生长动力学。结果表明,随着渗硼温度的升高或渗硼时间的延长,渗硼层的厚度不断增大,但当渗硼温度超过900 ℃时,渗硼层中黑色孔洞的数量、大小以及距离渗硼层表面的深度都逐渐增大。65Mn钢渗硼层都由Fe₂B柱状晶,以及位于Fe₂B柱状晶生长前沿及晶粒间的Fe₃(B,C)相、二元铁硅化合物和三元铁碳硅化合物组成,其维氏硬度(800~1590 HV0.05)远大于65Mn钢基体的硬度(238 HV0.05)。由于硬度较低的Fe₃(B,C)相和富硅相分布于高硬度的Fe₂B柱状晶晶粒之间,导致渗硼层的硬度并不随离渗硼层表面距离的增加而单调减小。渗硼层厚度的平方与渗硼时间呈线性关系,B原子在65Mn钢渗硼层中的扩散激活能为220.96 kJ/mol。     

La2O3包埋渗硼TB2钛合金的腐蚀与磨损性能

为了改善TB2合金的表面性能,采用4％La2O3(质量分数)包埋渗硼法对TB2合金进行1100℃,20 h渗硼处理,研究TB2钛合金的渗硼层组成与厚度以及腐蚀与磨损性能.结果表明,La2O3在渗硼过程中促进硼化物层的生长,提高其连续性和致密性,TiB晶须长度从16.80增至21.84μm.这是因为La2O3能与B反应生...     

2205双相不锈钢包埋粉末渗硼性能研究

目的 提高2205双相不锈钢的硬度和耐蚀性能.方法 2205双相不锈钢采用固体包埋粉末渗硼,于马沸炉中分别在830、860、890℃下保温5 h;在860℃下保温3、5、7 h,随炉冷却到室温.用金相显微镜、扫描电镜观察渗硼层的形貌和测定渗硼层的厚度,用维氏硬度计测定渗硼层的硬度,用纳米压痕仪测定渗硼层不同深度的硬度,用X射线衍射仪分析渗硼层的物相组成,评定渗硼层与基体的结合力,做不同介质下耐蚀性对比试验.结果 渗硼层与基体结合牢固,破坏等级评为一级,渗硼层主要由Fe2 B单相组成.在860℃下保温不同时间,渗硼层的厚度及硬度均随时间的增长而逐渐增大;在不同温度下保温5 h时,渗硼层的厚度及硬度随温度的升高而逐渐增大.渗硼后试样在质量分数都为10%的HCl和NaCl溶液中耐蚀性提高,在质量分数均为10%的H2 SO4、NaOH和HNO3溶液中耐蚀性变差.结论 固体粉末包埋法渗硼工艺改善了2205双相不锈钢的表面组织和性能,有效提高了其硬度及耐蚀性.     

镁合金微弧氧化层上低温化学镀镍研究

研究了在镁合金微弧氧化陶瓷层上进行低温化学镀镍的工艺,并对镀层的成分、结构和耐蚀耐磨性能进行了分析。实验确定,在40℃左右对陶瓷层进行有效化学镀镍的镀液配方为:NiSO4.6H2O 40g/L,NaH2PO2.H2O 40g/L,(CH2CH2OH)310mL/L,C6H8O7.H2O 7.5g/L,NH4HF 20g/L,用NH3.H2O调节pH值保持在9.5左右。采用上述镀液在40℃施镀,得到的镀镍层为低磷微晶结构,与陶瓷层结合紧密且对陶瓷层有封孔作用,耐蚀和耐磨性能良好。     

新型Te-Ni-Cr合金在Na2SO4-25％NaCl熔盐中的腐蚀行为

利用粉末冶金技术制备了新型Te-Ni-Cr合金材料.通过静态质量损失试验,X射线物相分析,扫描电镜形貌观察及微区成分分析等手段,研究了合金在750℃Na2SO4-25wt％NaCl熔盐中的热腐蚀行为及热腐蚀动力学规律.研究表明:稀有元素碲的加入,使合金的腐蚀速率较Ni-Cr合金有比较明显的下降;随时间的延长,合金表面的腐蚀程度不断增加;腐蚀产物主要为铁的氧化物、镍及铬的硫化物和氧化物;热腐蚀层主要由铁的氧化物和CrO3组成.     

热电池用导电镍带的高温硫化行为研究

应用SEM、XRD、EDS等技术研究了高纯镍（0号镍）和杂质含量较高的工业镍N6在1 kPa,300~500℃的硫蒸气中的高温硫化行为。结果表明,在300℃两者都抗硫化,400℃两者都显著硫化,动力学近似遵从抛物线法则,高纯镍在500℃变为直线法则。动力学曲线拟合结果表明,400℃以上N6镍的腐蚀速度常数K要比高纯镍小约1个数量级,杂质对降低N6镍的腐蚀速度有重要作用。     

The effect of boron-pack refreshment on the boriding of mild steel by the spark plasma sintering (SPS) process

Mild steel samples were borided with and without boron pack refreshment using the spark plasma sintering (SPS) process. Results show that the borided samples with boron pack refreshment developed a thicker boride layer compared to that without boron pack refreshment for the same boriding duration. When boriding duration is t < 120 min, the boriding growth in the samples borided with boron pack refreshment followed a parabolic growth pattern. In contrast, the boride growth in samples processed without boron-pack refreshment deviates from parabolic at t = 60 min. Computer simulation shows that the boron concentration change in the boriding media during the boriding process is an important factor affecting the composition and final thickness of the boride layer.     

Characterization of borided pure molybdenum under controlled atmosphere

In this study, the structural characterization and boriding kinetics of the molybdenum borides formed on the surface of borided pure molybdenum (Mo) have been investigated. Boronizing was carried out in solid medium with boron component forming Ekabor ® 2 (90% SiC, 5% KBF₄, 5%B₄C) powders at 1273 K, 1373 K for 2, 4, 6, 8 hours under a controlled atmosphere containing argon gas flow. The boride layer was characterized by the scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Energy dispersive spectroscopy (EDS) and Vickers microhardness tester. X-ray diffraction analysis showed that the boride layers on molybdenum consisted of MoB and Mo₂B phases. However, the MoB phase was observed at certain boriding temperature and boriding times. The thickness of boronized layers almost ranged from 12 to 42.5 μm with boriding time. A parabolic relationship was observed between boride layer thickness and boriding time. The growth rate constant and activation energy for the boride layer were calculated. The hardness of borides compounds formed on the surface of molybdenum ranged from 925 to 1150 HV_0.05, whereas the hardness of the untreated molybdenum sample was 258 HV_0.05.     

Influence of nickel silicides presence on hardness,elastic modulus and fracture toughness of gas-borided layer produced on Nisil-alloy

The two-stage gas boriding in N₂?H₂?BCl₃ atmosphere was applied to producing a two-zoned borided layer on Nisil-alloy. The process was carried out at 910 °C for 2 h. The microstructure consisted of two zones differing in their phase composition. The outer layer contained only a mixture of nickel borides (Ni₂B, Ni₃B) only. The inner zone contained additionally nickel silicides (Ni₂Si, Ni₃Si) occurring together with nickel borides. The aim of this study was to determine the presence of nickel silicides on the mechanical properties of the borided layer produced on Ni-based alloy. The hardness and elastic modulus were measured using the nanoindenter with a Berkovich diamond tip under a load of 50 mN. The average values of indentation hardness (H_I) and indentation elastic modulus (E_I) obtained in the outer zone were respectively (16.32±1.03) GPa and (232±16.15) GPa. The presence of nickel silicides in the inner zone reduced the indentation hardness (6.8?12.54 GPa) and elastic modulus (111.79?153.99 GPa). The fracture toughness of the boride layers was investigated using a Vickers microindentation under a load of 0.981 N. It was confirmed that the presence of nickel silicides caused an increase in brittleness (by about 40%) of the gas-borided layer.     

P91钢亚音速喷涂NiCr/Cr3C2涂层的热腐蚀行为研究

采用亚音速火焰喷涂方法在P91钢上制备了NiCr/Cr3C2涂层,研究了样品在600,650和700℃的80 ％Na2 SO4 +10％K2SO4+10％KCl(质量分数,后同)混合熔融盐中的热腐蚀行为,利用XRD和SEM分析了表面成分和结构.结果表明:喷涂NiCr/Cr3 C2涂层样品在热腐蚀过程中,腐蚀产物从样品表...     

不同锰含量的Fe-Cr-Mn三元合金耐锌蚀能力

研制了4种Mn含量不同的Fe-Cr-Mn三元合金,并系统研究和分析了其在450℃熔融锌液中的腐蚀行为及组织变化规律。结果表明,4种不同锰含量的Fe-Cr-Mn三元合金腐蚀层的形貌基本相似,但与纯铁在液锌中的腐蚀形貌差别很大,其主要是由致密的δ相层和分布于η相中稀疏的ζ相颗粒组成,且δ相层厚度随锰含量的提高先增加后减少,其中属含Mn量为9.55%的Fe-Cr-Mn三元合金腐蚀层中致密的δ相层厚度最厚,表现出较好的耐锌蚀能力,同时,此三元合金基体与腐蚀层界面处存在Cr的富集区,此区约含27.48%的Cr,厚度在1μm左右。连续完整的富Cr抑制层的形成,能够减缓铁锌反应的速度,减慢对基体的腐蚀速度,提高了耐锌蚀能力。     

直流电场增强粉末渗硼特性研究

将20钢和45钢试样置于渗罐中平行的板状正负电极上及靠近和远离电极的部位,并施加一直流电场,以研究800℃时直流电场在粉末渗硼中的作用。试验结果表明,直流电场对渗罐内不同位置试样及同一试样的不同部位的渗硼作用不同,远离电极的试样渗硼速度比常规渗硼的还要低;从正极到负极,直流电场的促渗作用逐渐增强,直流电场促进试样渗硼的作用主要表现于面向正极的试样面。这种结果是由直流电场对渗硼过程中渗剂的化学反应、含硼活性基团及硼的扩散的影响所决定的。     

Investigation of the diffusion kinetics of borided stainless steels

In this study, the kinetics of borides formed on AISI 420, AISI 304 and AISI 304L stainless steels was investigated. Boronizing treatment was carried out using Ekabor-II powders at the processing temperatures of 1123, 1173 and 1223 K for 2, 4 and 6 h. The phases of the boride layers of borided AISI 420, AISI 304 and AISI 304L stainless steels were FeB, Fe₂B, CrB and NiB, respectively. The thickness of the boride layer formed on the borided steels ranged from 4.6 to 64 μm depending on the boriding temperature, boriding time and alloying elements of the stainless steels. Depending on the chemical composition, temperature and layer thickness, the activation energies of boron in AISI 420, AISI 304 and AISI 304L stainless steels were found to be 206.161, 234.641 and 222.818 kJ/mol, respectively. The kinetics of growth of the boride layers formed on the AISI 420, AISI 304 and AISI 304L stainless steels and the thickness of the boride layers were investigated.     

The investigation of corrosion behavior of borided AISI 304 austenitic stainless steel with nanoboron powder

In this study, corrosion behavior and mechanical properties of AISI 304 austenitic stainless steel, which was borided with Nanoboron powder, was investigated. The commercially available steel was subjected to a boriding treatment with a size of 10–50 nm Nanoboron powders, at the temperatures of 1223 K to 1273 K with boriding durations of 2 to 4 h. Microstructure characterization of the steel was carried out with optical microscopy, scanning electron microscopy, microhardness and X-ray diffraction analyses. Corrosion tests were made by static immersion into a 10% H₂SO₄ acid solution and weight loss calculations as well as salt spray tests were carried out in accord with the ASTM B-117 standard. Boriding thermal treatment, increased the corrosion resistance of the steel against the acid solution, up to about 4.3 times while in the salt spray tests, weight loss corrosion resistance increased up to tier 2. However, anti-corrosion resistance decreased by 40%, its untreated value.     

铁基粉末冶金材料渗硼强化的干滑动高温摩擦磨损行为

通过固体粉末渗硼法直接烧结铁基粉末冶金材料,制备具有渗硼层的试样。将铁基粉末冶金材料在850、950和1050 ℃渗硼处理3、5和10 h,采用光学显微镜及扫描电镜观察了渗硼层的形貌,测定了渗硼层的厚度;用 X 射线衍射仪分析了渗硼层的物相组成;用Rockwell-C粘附性试验评估渗硼层与基体的粘合强度质量。使用 HT-1000 型高温摩擦磨损试验机测试了试样的摩擦磨损性能。结果表明,在850 ℃及950 ℃下渗硼形成单相Fe₂B,而FeB+Fe₂B双相渗硼层在1050 ℃下生成。粘附性试验与高温磨损试验均表明,在950 ℃下渗硼5 h的试样的渗层与基体结合最为紧密,抗磨损及抗氧化的能力最强。高温摩擦磨损试验中,微裂纹引起的分层剥落及氧化磨损是渗硼试样主要的磨损机制,未渗硼试样出现严重的的氧化和塑性变形。     

纳米 NiCrBSi-TiB2 涂层在硫酸熔盐中的热腐蚀行为研究

目的研究纳米NiCrBSi-TiB2涂层在800℃下的Na2SO4-30%(质量分数)K2SO4熔盐中的热腐蚀行为。方法采用超音速火焰技术在中碳钢表面喷涂纳米NiCrBSi-TiB2涂层,以饱和Na2SO4-30%K2SO4溶液为腐蚀介质,研究该涂层在800℃时的热腐蚀行为。结果微米涂层晶粒粗大,Si的扩散系数低,易出现贫Si富Cr层,形成的Cr2O3膜在碱性熔盐中具有较低的溶解度,对涂层具有良好的保护作用。结论微米涂层在Na2SO4-30%K2SO4熔盐中具有更优的抗热腐蚀性能。     

超音速喷涂45CT涂层在KCl+K2SO4+Na2SO4熔融盐中的热腐蚀行为

目的研究超音速喷涂45CT涂层抗KCl+K_2SO_4+Na_2SO_4熔融盐腐蚀性能,了解45CT涂层在熔融盐中的防护及失效机制。方法将试样置于KCl+K_2SO_4+Na_2SO_4混合熔盐中,获得样品在熔盐中不同温度下的腐蚀动力学规律。采用XRD、SEM、EDS对高温腐蚀产物成分、结构、形貌进行分析。结果 45CT涂层在熔融盐中的主要腐蚀产物为Cr_2O_3、NaCrO_2。在600℃和650℃下,涂层能较好地保护基体,涂层上腐蚀产物层较薄;而在700℃下,涂层退化严重,涂层内有大量金属硫化物,基体中的Fe向涂层扩散。结论在高温条件下,涂层易发生硫化,导致涂层与氧化膜的弱结合。随着测试温度升高,涂层在KCl+K_2SO_4+Na_2SO_4熔融盐中的热腐蚀越严重,涂层失效加快。     

超超临界锅炉用TP310HCbN不锈钢的热腐蚀行为研究

以80%Na2SO4+10%K2SO4+10%KCl混合熔融盐为热腐蚀介质,研究了TP310HCbN奥氏体不锈耐热钢在600℃,650℃和700℃下的热腐蚀行为。结果表明:在600℃和650℃下,腐蚀失重轻微,热腐蚀过程中腐蚀产物从样品表面剥落,样品晶界发现大量硫化物,并有明显的晶间腐蚀倾向;在700℃下,样品失重加速,腐蚀产物剥落严重。利用XRD和SEM分析样品经热腐蚀后的表面成分和结构,腐蚀产物主要由Fe3O4和(Fe,Cr)2O3组成,并含有少量的NiCr2O4和Cr2S3。     

Ni/AlN Composite Coating for Corrosion and Elements Interdiffusion Resistance in Molten Fluoride Salts System

The Ni/AlN composite coating was prepared for increasing corrosion and elements interdiffusion resistance of GH3535 alloy in molten fluoride salts,and the effect of mechanical interlocking on adhesion strength between AlN layer and nickel coating was also studied.Results indicated that the adhesion strength between AlN layer and nickel coating could be signifi-cantly enhanced through mechanical interlocking effect,which effectively prevented the nickel coating from flaking off at elevated temperature.Through an etching pre-treatment of AlN layer,the corrosion resistance of the Ni/AlN coated GH3535 alloy in molten FLiNaK salt was further improved,and elements interdiffusion between the substrate and nickel coating was completely suppressed.AlN layer as a diffusion barrier remained compact and continuous in Ni/GH3535 system after high-temperature molten salt corrosion.Moreover,a Ni-P layer consisting of Ni3P and Ni phases formed in the Ni coating after corrosion.