TC4合金表面激光熔覆B4C及B4C＋Ti粉末涂层的微观组织

利用XRD，SEM和EDS分析手段对B4C和B4C＋10％Ti（质量分数，下同）激光熔覆层的微观组织进行了分析。结果表明，TC4合金表面B4C与B4C＋10％Ti激光熔覆层的组成相基本相同，均由TiC1-x，TiB，TiB2和Ti相组成，说明在TC4合金表面熔覆过程中有一部分Ti进入熔覆层并与B4C发生化学反应原位生成了TiB，TiB2和TiC1-x相。TiC1-x相以树枝状相形式存在，TiB2相以粗大须状相形式存在，TiB相以细小须状相形式存在。熔覆层与基底结合良好，没有发现裂纹与孔洞。基底热影响区呈淬火组织形貌，为典型的针状马氏体组织特征。与B4C激光熔覆层相比，B4C＋10％Ti激光熔覆层的组织细小，TiB相含量增多，TiB2相含量减少。     

TC4钛合金激光熔覆TiC+M涂层组织和耐磨性能研究

用CO2激光在TC4合金表面熔覆TiC＋髓和TiC＋NiCrBSi金属陶瓷涂层,分析了熔覆层的微观组织,测试了熔覆层的干滑动磨损性能。结果表明,在TiC＋Ti激光熔覆层中,TiC颗粒全部溶解,熔覆层的组织是在β-Ti基体上分布着TiC树枝晶;在TiC＋NiCrBSi激光熔覆层中,TiC颗粒部分溶解,熔覆层的组织是在γ-Ni树枝晶和卜Ni＋M23（CB）6共晶的基体上分布着细小的TiC颗粒和TiC树枝晶。TiC＋骶激光熔覆层的显微硬度在500～700HV之间,质量磨损率约为TC4合金的1／3;TiC＋NiCrBSi激光熔覆层的显微硬度在900～1100HV之间,质量磨损率约为TC4合金的1／10。     

Ti6Al4V表面激光熔覆原位自生TiC颗粒增强钛基复合材料及摩擦磨损性能

以Ti,Cr3C2混合粉末作为预置合金涂层,采用YAG固体激光器进行激光熔覆处理,在Ti6Al4V合金表面制备出原位自生TiC颗粒增强钛基复合材料涂层,实验结果表明,采用合适的合金粉末成分和激光辐照能量密度,可以获得增强相TiC弥散分布的钛基复合材料熔覆层,熔覆层结晶致密,且与复合材料基体润湿性良好,熔覆层复合材料的基体组织随预置合金粉末成分的改变而变化,摩擦磨损实验结果表明,原位自生TiC/Ti复合材料熔覆层可明显改善Ti6Al4V合金的表面硬度和摩擦磨损性能。     

激光熔覆原位自生Fe-Ti-B系复合涂层物相组织研究

采用钛铁、硼铁为预置粉末,利用激光熔覆搭接技术在碳钢基体上制备了Fe-Ti-B系原位自生颗粒增强Fe基复合涂层。利用X射线衍射仪、光学显微镜、扫描电镜、电子探针对熔覆层的相组成和显微组织进行了研究,并用洛氏硬度计测量了涂层硬度。结果表明,涂层中原位自生的增强粒子包括TiB2、FeB、Fe2B和Fe2Ti。且随着涂层中Ti,B原子比例的不同,涂层的相结构发生相应演变。当涂层增强相为FeB＋Fe2B＋TiB2和TiB2＋Fe2Ti时,涂层的塑性降低,在激光熔覆应力的作用下产生裂纹,当涂层增强相为Fe2B＋TiB2及TiB2,可获得致密、无缺陷的熔覆层。同被强化基体相比,熔覆层硬度有较大提高,且增强相为FeB＋Fe2B＋TiB2的涂层具有最高的硬度。     

Ti6Al4V合金表面氩弧熔覆原位合成TiC-TiB2增强钛基复合涂层组织与耐磨性

以B4C和Ni60A粉末为预涂材料,采用氩弧熔覆技术,在Ti6Al4V合金表面原位合成TiC与TiB₂增强相增强钛基复合材料涂层.运用XRD,SEM等分析手段研究了复合涂层的显微组织,利用显微硬度仪测试了复合涂层的显微硬度并用磨损试验机分析了其在室温干滑动磨损条件下的耐磨性能.结果表明,熔覆层组织主要由TiC和TiB₂组成,TiC颗粒和TiB₂颗粒弥散分布在基体上,TiC颗粒的尺寸为2~3μm,而呈长条状的TiB₂颗粒尺寸为3~5μm.显微硬度和耐磨性测试结果表明,该复合涂层显微维氏硬度高达1200MPa左右,复合涂层的耐磨性能比Ti6Al4V基体提高约20倍.     

钛合金表面等离子弧熔覆原位自生镍基耐磨涂层的制备及微观结构表征

目的 在钛合金表面制备陶瓷相增强复合耐磨涂层。方法 采用等离子弧熔覆技术,在Ti6Al4V钛合金表面制备了原位自生TiB2、TiC、CrB陶瓷相增强镍基耐磨涂层。采用X射线衍射仪、扫描电镜、能谱仪检测了涂层的物相组成、组织组织以及微区化学成分,采用显微硬度计测试了涂层的硬度。结果 涂层靠近熔合线区域由Ni-Ti树枝晶及枝晶间的共晶组成,在涂层的中上部,大量原位增强相分布于镍基固溶体基体之中。在熔覆过程中,钛合金基材中的Ti元素同熔覆粉末中的B、C元素发生原位冶金反应形成TiB2、TiC增强相,CrB增强相为Ni基熔覆粉末中Cr、B元素反应形成,增强相的形态由各自的晶体结构及熔池凝固热力学与动力学条件决定。涂层的显微硬度得到显著提高,最高达1037HV0.2。结论 采用等离子弧熔覆技术,利用熔池内Ni-Cr-Ti-B-C合金体系的原位冶金反应,可以在钛合金表面制备原位自生TiB2、TiC、CrB增强镍基复合耐磨涂层。同Ti6Al4V基材相比,由于涂层具有大量增强相分布于镍基固溶体的组织特征,其显微硬度得到了显著提高。     

Ti6Al4V表面激光熔覆NiCrBSi+B4C涂层的工艺研究

采用JG-Ⅱ型CO2工业激光器,选用不同配比(均采用质量配比)的NiCrBSi和B4C粉末在TC4合金表面进行激光熔覆处理,通过原位自生法制备出TiC与TiB2等增强相增强钛基复合材料涂层;研究了激光熔覆工艺参数对熔覆层质量及稀释率的影响.结果表明:激光熔覆层的宏、微观质量与熔覆材料种类和激光熔覆工艺参数密切相关;在优化的激光工艺参数:P=750 W,d=3 mm,δ=0.8 mm(NiCrBSi+2%B4C混粉),δ=0.6 mm(纯NiCrBSi粉),v=5 mm/s时,获得了激光熔覆层表面连续均匀、内部无裂纹和气孔且与基底实现冶金结合的NiCrBSi和NiCrBSi+2%B4C激光熔覆层.     

TC4钛合金表面激光熔覆复合涂层的组织和耐磨性

采用5 kW横流CO₂激光器,在TC4钛合金表面熔覆TiC、TiB₂与Ni的混合粉末,制备了无气孔、无裂纹、组织均匀致密的复合涂层。用SEM、EDS、XRD、显微硬度计以及立式万能摩擦磨损试验机分析了激光熔覆层的显微组织、成分和物相,测试了激光熔覆层横截面显微硬度,以及覆层耐磨性能。结果表明,激光熔覆复合涂层与基体呈冶金结合;熔覆层组织从表层到结合区呈现出由棒状、块状向树枝状、颗粒状转变的趋势,且主要由Ti、TiC、TiB、Ti₂Ni、TiNi等相组成;熔覆层显微硬度最高可达863 HV0.2,为基体的2.5倍;熔覆层耐磨性能较TC4钛合金明显提高。     

钛合金表面激光熔覆复合涂层的显微组织与性能

以Ti和B的混合粉末为原料,采用激光熔覆方法在Ti-6Al-4V基体表面激光熔覆制备了TiB/Ti复合涂层。采用XRD、扫描电镜、硬度测试和摩擦磨损分析等方法研究了不同激光功率参数下制备的TiB/Ti复合涂层的物相结构、显微组织、硬度和耐磨性能。结果表明:涂层的物相组成主要为Ti和TiB两相;扫描功率为3000 W和3500 W下激光熔覆层的组织较均匀;扫描功率为2500 W和3500 W制备的涂层硬度值约为基体硬度的2～3倍;扫描功率为3000 W下的熔覆涂层硬度相对较高,其平均硬度值约为1199.6 HV0.2,约为基体硬度的3～4倍,其摩擦系数大约为0.32,磨损率明显低于基体,约为基体的14.8%。     

Ti6Al4V合金表面激光熔覆钛基复合涂层的显微组织研究

在Ti6Al4V合金表面预置Ti和Cr3C2混合粉末,采用横流CO2激光进行熔覆试验,制备出了原位自生的TiC颗粒增强的钛基复合涂层.利用SEM、XRD等手段对激光熔覆层的组织、成分、物相进行了分析,测试了激光熔覆层的显微硬度.结果表明,熔覆层不同位置,组织形态不同,TiC在熔覆层表层以树枝晶形态存在,而在熔覆层底部为近球状颗粒.熔覆层与基材之间形成良好的冶金结合.熔覆层显微硬度在600～800 HV0.5之间,约为基材硬度的2～3倍.     

SrxBa1-xBi4Ti4O15陶瓷及SrBi4Ti4O15／BaBi4Ti4O15复合材料的性能研究

采用固相烧结工艺制备了SrxBa1-xBi4Ti4O15铁电陶瓷和SrBi4Ti4O15／BaBi4Ti4O15铁电复合材料。在固相反应过程中，680℃时SrBi4Ti4O15或BaBi4Ti4O15开始生成：800℃时材料主晶相基本形成，但是还有微量焦绿石相存在；850℃时SrBi4Ti4O15或BaBi4Ti4O15的主要衍射峰全部出现。随着Ba含量的增加，SrxBa1-xBi4Ti4O15陶瓷的居里温度逐渐降低。Sr0.5Ba0.5Bi4Ti4O15，陶瓷的介电常数峰在高频时较宽，在100Hz时，介电常数峰被随温度升高而逐渐增大的介电常数所“屏蔽”，材料介电损耗随温度升高而增大，但在低频下增加得更快，这是高温下由氧空位引起的电子松弛极化造成的。将预烧后的SrBi4Ti4O15和BaBi4Ti4O15粉体分别造粒后冉均匀混合，压片成型，经烧结制得的SrBi4Ti4O15／BaBi4Ti4O15复合陶瓷其相变弥散特性明显优于SrxBa1-xBi4Ti4O15的相变弥散特性。     

快速凝固Al—4Cr—4Zr—2Ti合金的时效特性

利用透射电镜观察了Al-4Cr-4Zr-2Ti（原子百分比）合金的显微组织,并测定了相应的显微硬度。结果表明：快凝合金在400℃,4h时效达到峰值硬度,Hv达2420MPa,此时的析出相为Al13Cr2和与基体共格的亚稳相Ll2-Al3Zr。合金经400℃,96h时效后的显微硬度与急冷态硬度和峰值硬度相比仅分别下降10％和14％。而500℃,4h时效后,由于Ll2-Al3Zr转变为DO23－Al3Zr并且析出相粗化,导致合金硬度急剧下降。     

Inhibierung von wässerigen und alkoholisch wässerigen Wärmeträgern

Inhibition of aqueous and alcoholic-aqueous heat-carriers To examine the effect of corrosion inhibitors mainly ®Preventol CI-2 in aqueous and aqueous alcoholic heat transfer media gravimetric and electrochemical corrosion tests were carried out with the materials grey cast iron, unalloyed steel, copper, brass, lead-tin-solder, aluminium and aluminium alloys up to a temperature of 90°C. In the presence of the inhibitor Preventol CI-2 uniform layers from 10 to ? 50 nm thickness are found on the metal surfaces and the measured massloss (ASTM, EMPA) decreased decidedly. Local corrosion as occurs e.g. by insufficient concentration of inhibitors forming surface layers, was found in none of the cases. The electrochemical examinations confirm the results of the chemical tests and provide indications with regard to the effective mechanisms. The influence of temperature and flow rate on the protective efficiency of the inhibitor can be showed. It is possible to eliminate the risk of galvanic corrosion by contacting copper and aluminium. The cavitation corrosion of grey cast iron is also appreciably reduced. Preventol CI-2 is a broad spectrum inhibitor for aqueous and aqueous alcoholic heat transfer media.     

Homogenität und Korrosionsbeständigkeit hochlegierter Stähle

Homogeneity and corrosion resistance of high alloy steels A major number of case histories in the chemical industry are due to local corrosion the origin of which can be attributed to the inhomogeneity of the steels produced according to conventional melting process. Special processes such as electro slag remelting may give rise to a considerable increase in structural homogeneity of corrosion resistant alloys. Typical examples are increased resistance to nitric acid, Streicher's solution, seawater or reaction mixtures of urea synthesis. These results clearly demonstrate the superiority of the material which is largely free from inhomogeneities such as segregations which give rise to local corrosion phenomena.     

Order-disorder phase transition in NH4AlF4

In this study we calculate the specific heat C_VI for NH₄AlF₄ due to the nearest-neighbor interactions between the NH⁺ ₄ tetrahedra using an Ising model superimposed on an Einstein and/or Debye model. The specific heat C_VI calculated using a power-law formula is in good agreement with the observed C_P for the NH₄AlF₄ system. This is an indication that NH₄AlF₄ undergoes a weak first-order or a nearly second-order phase transition as predicted by our model.     

Widerstandsfähigkeit hitzebeständiger Stähle gegen Aufkohlung

Cementation resistance of heat-resistant steels The cementation process in atmosphere used for the cementation of unalloyed and low-alloyed steels has been examined in 79 melts of Cr and CrNi steels. A characteristic feature was the simultaneous cementation and oxidation of the steels, with characteristic differences depending on the steel composition. These differences can be explained by the different composition and structure of the oxide layers which appear at the outset and may, in certain circumstances, inhibit the carbon diffusion into the interior of the metal. Sometimes, however, an inner oxidation may also occur below a cemented zone. In principle, elements capable of improving the heat resistance — e.g. Ni, Si, Cr, Al — have a favourable effect whilst Mn has a markedly unfavourable effect. The favourable effect of Ti, recently observed, is probably connected with the grain-refining effect.     

SKT4

正SKT4钢具有良好的韧性、强度和高耐磨性;在室温和500~600℃时力学性能几乎相同,加热到500℃时,仍能保持住300 HB左右的硬度;由于钢中含有钼,因而对回火脆性并不敏感;从600℃缓慢冷却下来后,冲击韧性仅稍有降低;具有良好的淬透性,300 mm×400 mm×300 mm的大块钢料,自820℃油淬和560℃回     

YXM4

正YXM4为钨钢高速度钢,适宜于制造强力切割用耐磨,耐冲击各种工具,高级冲模,螺丝模,较需韧性及形状繁杂工具,铣刀,钻头等。化学成份(%):0. 87～0. 95 C;0. 45 Si;0. 40 Mn; 3. 80～4. 50 Cr; 5. 90～6. 70 W; 1. 70～2. 10 Mo;4. 80 V。热处理:锻造温度1100～900℃;退火温度800～850℃,保温2～4 h后随炉冷却;淬火温度,先预热至550～600℃,二次预热至950℃,再加热至奥氏体温度1220～1250℃或1200～1230℃,油淬,油温必须40～60℃;回火温度550～570℃,在静止空气中冷却,重复二次;硬度63 HRC以上;退火硬度265 HBS,淬火回火硬度 63 HRS。     

Phase diagrams of Li2MoO4-Na2MoO4 and Na2MoO4-K2MoO4 systems

The phase diagrams of the Li2MoO4-Na2MoO4 and Na2MoO4-K2MoO4 systems have been reassessed using differential thermal analysis together with high-temperature and room-temperature X-ray diffraction analysis. The results showed that the compound Li2MoO4.6Na2MoO4 did not exist; however, it confirmed the existence of the compound Li2MoO4.3Na2MoO4 in the Li2MoO4-Na2MoO4 systen＇ls. With regard to the system of Na2MoO4-K2MoO4, we could not confirm the results reported by Bukhanova who claimed that the system was eutectic type with 1：1 and 1：2 intermediate compounds, refuting the statement of Amadori who thought there was an apparent phase boundary at high temperature in α-solid solution region of the Na2MoO4-K2MoO4 binary system. The revised phase diagrams of these systems are illustrated in this article. These experimental results are in agreement with the computerized prediction using the support vector machine-atomic parameter method for the assessment of phase diagrams.