铬钼钢制加氢换热器,反应器耐蚀层堆焊质量分析

依据焊接试验与产品应用结果，从焊接试验与产品堆焊的全过程出发，论述了堆焊工艺应用范围、耐蚀层堆焊的技术要求、堆焊工艺参数的选择以及堆焊层的质量问题，重点分析失效现象及产生原因，并提出了防止措施。     

碳化铬对H13钢镍基等离子弧堆焊覆层组织与硬度的影响

热锻模长期在高温环境中承受较大机械载荷以及冷热疲劳等作用,容易发生破坏失效。通过等离子粉末堆焊在模具表面上堆焊制备出高性能表面覆层,大幅度提高了模具性能。通过对复合材料的制备方案的分析,选择镍基自熔性合金粉末,借助等离子粉末堆焊工艺制备出碳化铬增强镍基堆焊覆层。以H13钢为例,对比研究了镍基合金堆焊层以及镍基碳化铬堆焊层的组织成分、相结构及显微硬度。堆焊层的微观组织表明,堆焊层与基体冶金结合良好,堆焊层熔接线附近元素呈梯度分布。镍基堆焊层以及镍基碳化铬堆焊层组织均以γ-Ni固溶体为主,在晶界处分布有碳化物和硼化物。由于碳化铬颗粒的强化作用,镍基碳化铬堆焊层中的固溶体晶粒更加细小,同时碳化物数量更多,弥散分布在固溶体的晶界处。     

WC耐磨堆焊层表面缺陷的激光熔覆修复

堆焊层表面不可避免地存在孔洞、半埋藏裂纹缺陷,理论分析与数值模拟表明,缺陷会引起应力集中,当裂纹尖端的应力强度因子值达到断裂韧性时,裂纹会失稳扩展,导致材料的实际断裂强度远低于该材料的理论断裂强度,使构件很快失效。激光熔覆利用高能量的激光束使存在缺陷的堆焊层表面熔化再结晶,并用合金粉末在表面涂覆一层合金层,实验研究发现,堆焊层与熔覆层呈冶金结合,熔覆层并未影响到堆焊层高硬度的特性。超声波无损检测结果表明,堆焊层表面的孔洞、半埋藏裂纹缺陷已基本被消除,达到了强化与修复的目的。     

电火花堆焊修复不锈钢表面缺陷工艺

针对飞机不锈钢材料表面损伤,采用电火花堆焊技术进行修复,研究堆焊工艺参数对堆焊过程工艺性、修复层成形性及其显微组织的影响。结果表明,修复层与基体组织呈冶金结合。输出电压是电火花大小和堆焊速度的主要影响因素,最优的输出功率和电压组合为:功率500 W,电压66 V;功率1 000 W,电压89 V;功率1 500 W,电压46 V。脉冲频率高时的堆焊成形性比脉冲频率低时要好。电极直径1.5 mm比4 mm的成形组织更好。修复层的硬度相比基体有显著提高,可达到360 HV。     

超低碳氮强化药芯焊丝堆焊层组织与性能

采用自主研制的超低碳氮强化药芯焊丝,利用明弧摆动堆焊技术,选择合适的堆焊工艺参数,在42CrMo板表面堆焊形成马氏体不锈钢堆焊层。通过超声波探伤仪、金相显微镜、EDS、显微硬度计分析测试堆焊层的组织、成分及性能。结果表明,堆焊层无裂纹、气孔等缺陷,与母材达到了冶金结合;堆焊层组织为单一的马氏体,其成分与所设计的药芯一致;堆焊层的硬度从底部到表层呈梯度变化,其平均硬度是基体的2.5倍,弥补了传统堆焊材料整体韧性不足的缺陷;氮化物均匀弥散分布在堆焊层表面。     

超低碳氮强化药芯焊丝堆焊层组织与性能

采用自主研制的超低碳氮强化药芯焊丝,利用明弧摆动堆焊技术,选择合适的堆焊工艺参数,在42CrMo板表面堆焊形成马氏体不锈钢堆焊层。通过超声波探伤仪、金相显微镜、EDS、显微硬度计分析测试堆焊层的组织、成分及性能。结果表明,堆焊层无裂纹、气孔等缺陷,与母材达到了冶金结合;堆焊层组织为单一的马氏体,其成分与所设计的药芯一致;堆焊层的硬度从底部到表层呈梯度变化,其平均硬度是基体的2.5倍,弥补了传统堆焊材料整体韧性不足的缺陷;氮化物均匀弥散分布在堆焊层表面。     

激光表面熔覆技术提高斯太尔曲轴模具寿命的研究

为了提高斯太尔曲轴模具的使用寿命,在斯太尔曲轴模具材料5CrMnMo钢的堆焊层表面进行了激光合金化处理实验.通过工艺实验,分析了堆焊层激光合金化处理后的组织和显微硬度;通过优化工艺参数,获得了表面光洁、与基材形成良好冶金结合的模具表面强化层;合金强化层平均硬度达到HV0.2750.激光表面熔覆技术已应用于热锻模具,使斯太尔曲轴模具寿命提高了60％.     

铝青铜与低碳钢等离子堆焊工艺研究

为了改善低碳钢的耐磨性,在其表面等离子堆焊一层铝青铜.对堆焊层的硬度、耐磨性和显微组织,以及界面的结合情况进行分析,研究堆焊工艺参数对堆焊层组织性能的影响规律,以确定最佳堆焊工艺参数.结果表明,当堆焊电流为110A时,堆焊层力学性能达到最佳值,堆焊层的硬度为259 HV,磨损量为0.008g,摩擦系数约为0.3,耐磨性最好.这主要得益于此时堆焊层中细小的α-Cu和弥散分布的β'相,它们有效地分散和传递了作用力,提高耐磨性.     

等离子原位合成陶瓷相增强铁基堆焊层

采用等离子堆焊技术,在碳钢基体表面预涂一定混合比例的高碳铬铁、钒铁和石墨,制备原位自生陶瓷相增强铁基堆焊层,并对堆焊层的组织和性能进行测试.结果表明:堆焊层与基体之间形成良好的冶金结合,堆焊层微观组织由马氏体、少量残余奥氏体、(Fe,Cr,V)7C3和VC构成.初生(Fe,Cr,V)7C3呈六边形,晶粒尺寸较大,均匀弥散分布在熔覆层中,VC颗粒呈团聚状或球状,晶粒较细小.堆焊层硬度从基体到表面呈合理的梯度分布,使材料具有较好的耐磨性.     

异种材质堆焊层组织及耐磨性

在不同堆焊工艺参数下,采用反极性弱等离子弧在低碳钢表面堆焊铝青铜合金粉末.利用金相、扫描电镜(SEM)和X射线衍射(XRD)等方法对堆焊层金属的组织进行研究,同时测试堆焊层的硬度和失重量.结果表明,堆焊层金属与母材是冶金结合,堆焊层金属稀释率低.当堆焊层金属含有组织致密的α相或α相沿晶界析出呈网状分布时,堆焊层耐磨性显...     

高炉风口表面处理工艺的研究和应用

通过分析爆炸焊接工艺特点,研究了爆炸焊接工艺在制造高炉风口生的应用。结果表明,用铜板和耐磨合金板通过爆炸焊接而在的耐磨复合板,具有结合强度高,导热性、耐磨性和可焊性好等特点,用于制作风口工作部位,使用安全、可靠、效果明显优于普通风口,具有良好的推广应用前景。     

高炉风口小套破坏机理和改用铍青铜材料的探讨

阐述了高炉风口小套材料的使用现状、使用工况和损坏原因.通过对紫铜风口小套侵蚀机理和铍青铜使用案例的分析得出,采用铍青铜替代紫铜生产高炉风口小套是可行的.如全国均采用铍青铜风口小套.每年可为国内钢铁企业节约铜耗费用3亿元,钢铁企业可多出250万吨以上铁水.     

堆焊铜合金/35CrMnSiA接头的界面结构特征

采用冷体TIG堆焊方法在钢质基体上堆焊铜合金层,重点分析了其微观组织.通过显微镜(OM)、扫描电镜(SEM)观察了界面、铜合金层及基体的组织形貌特征, 分析了焊接工艺对铜合金层中泛铁量的影响.通过能谱 (EDXA)研究了铜合金层内和界面的成分变化,发现在焊接过程中发生了基体元素向铜合金层中溶解和某些铜合金层元素向基体扩散,在由CuSi3形成的铜合金层中有Fe2Si生成,在由B30形成的铜合金层中存在树枝晶组织.而且,焊接工艺不当时,因界面处存在低熔共晶进而出现渗透裂纹.     

冷冲模具堆焊材料及堆焊工艺

针对冷冲模具的工作条件,失效形式和性能要求,研制了了ＣｒＭｏＷＶＴｉ合金系堆焊金属,并把它分别配制成钨极氩弧焊用药芯焊丝和焊条两种堆焊材料。     

堆焊双金属冷镦粗过程中的变形行为

借助冷镦粗实验研究堆焊双金属在大塑性变形下的变形行为,进而探索堆焊双金属坯料锻造成形的可行性。首先使用等离子弧喷焊技术制备双金属坯料,测定堆焊双金属熔覆层区域的显微硬度,认知堆焊双金属材料的界面特性;随后分析冷镦粗过程中堆焊双金属试样的变形与破坏方式。结果表明:堆焊双金属的显微硬度最薄弱区域出现在熔合线附近,熔覆层区域整体硬度远高于基体硬度;冷镦粗过程中,堆焊双金属基体区域率先发生塑性变形,熔覆层抵抗变形的能力高于基体;压缩到一定阶段,熔覆层底部区域也会发生塑性变形,熔覆层区域具有进行塑性变形的潜力。     

Characterization of Thermal,Mechanical and Tribological Properties of Fluoropolymer Composite Coatings

Perfluoroalkoxy (PFA) is a potential polymer coating material for low-temperature waste heat recovery in heat exchangers. Nonetheless, poor thermal conductivity, low strength and susceptibility to surface degradation by erosion/wear pose restrictions in its application. In this study, four types of fillers, namely graphite, silicon carbide, alumina and boron nitride, were introduced to enhance the thermal, mechanical and tribological properties in PFA coatings. The thermal diffusivity and specific heat capacity of the composites (reinforced with 20 wt.% filler) were also measured using laser flash and differential scanning calorimetry techniques, respectively. The results indicated that the addition of graphite or boron nitride increased the thermal conductivity of PFA by at least 2.8 orders of magnitude, while the composites with the same weight fraction of alumina or silicon carbide showed 20-80% rise in thermal conductivity. The micromechanical deformation and tribological behavior of composite coatings, electrostatically sprayed on steel substrates, were investigated by means of instrumented indentation and scratch tests. The deformation response and friction characteristics were investigated, and the failure mechanisms were identified. Surface hardness, roughness and structure of fillers influenced the sliding performance of the composite coatings. PFA coatings filled with Al₂O₃ or SiC particles showed high load-bearing capacity under sliding conditions. Conversely, BN- and graphite-filled PFA coatings exhibited lower interfacial adhesion to steel substrate and were prone to failure at relatively lower applied loads.     

Characterization of Low-Pressure Cold-Sprayed Aluminum Coatings

Aluminum alloys are widely used as materials for engineering components of automobiles and airplanes because of their light weight and high corrosion resistance. However, cracks may develop sometimes in aluminum components, which have to be repaired by welding. It is difficult to weld aluminum components due to its high specific thermal conductivity and high coefficient of thermal expansion. The low-pressure cold-spray technique can be used instead of welding for repairing cracks. However, the effects of surface conditions on particle deposition and the mechanical properties of cold-sprayed coatings have not been investigated thus far. In this study, the effect of surface conditions focusing on active newly formed surface on aluminum particle deposition is studied and the mechanical properties of low-pressure cold-sprayed aluminum coatings are investigated by four-point bending tests. It is found that for efficient particle deposition it was necessary to obtain active newly formed surface of the substrate and particle surfaces by several impingements because the existence of inactive native oxide films has an adverse effect on the deposition. Furthermore, the strength of a cold-sprayed specimen is found to be higher than that of a cold-rolled specimen under compressive loading.     

TIG torch surfacing of metallic materials – a critical review

This article aims to review and highlight the significant features and development of tungsten inert gas (TIG) torch surfacing of metallic materials. The emphasis is on the surfacing method for metallic materials using a melting processing route. The fusion surfacing methods such as powder injection, wire feed and pre-place powder are elaborated. The comparisons of TIG torch surfacing methods to electron beam welding, laser cladding and thermal spraying are tabulated to give a better understanding of each surfacing method. The application of TIG torch surfacing techniques on various metallic materials is reviewed based on a number of studies from previous researchers. The significance of processing variables of TIG torch surfacing techniques is highlighted with the heat input and welding speed being the most influential factors. This paper also shows the potential application of TIG torch surfacing for the hybridisation of composite coated hard surface layer formation in metallic materials.     

用于铸管模修复的抗热疲劳堆焊材料试验研究

通过铸管模的材质、服役条件、失效形式及失效机理分析,给出了用于铸管模修复的抗热疲劳堆焊材料研究试验方案.采用自约束热疲劳模拟试验方法研究了不同合金含量范围的耐热钢类堆焊材料对热疲劳性能的影响,为铸管模堆焊材料的细化研究打下了基础.研究表明,低合金耐热钢堆焊材料适用于铸管模的堆焊.     

热处理对氮化铝化学镀铜组织性能的影响

目的优化化学镀铜氮化铝(AlN)基板的综合性能,掌握热处理对其镀层致密度、界面结合强度和热导率的作用机理,并对划痕膜层失效行为进行分析。方法采用化学镀铜法实现AlN陶瓷基板表面金属化,对其进行200~500℃热处理。利用X射线衍射仪、扫描电镜、激光导热仪,对Cu-AlN基板的物相结构、显微形貌、热学性能进行分析。采用划痕法对镀层结合力进行评价,并通过划痕形貌对膜层失效行为进行分析。结果未热处理的Cu-AlN基板表面存在鼓泡现象,结合强度为24.7 N,热导率为156.8 W/(m K)。热处理消除了Cu-AlN基板的鼓泡现象,300℃热处理的Cu-AlN基板综合性能优异,表面Cu颗粒分布均匀,结构较为致密,结合强度为32.6 N,热导率达163.8 W/(m K);当500℃热处理时,Cu-AlN基板表面存在氧化现象,形成CuO,结合强度急剧降低为18.5 N,热导率为161.2 W/(m K)。Cu-AlN基板的基膜失效方式为点剥离,随着载荷的增加,点剥离增多,膜层开裂,AlN逐渐裸露,Cu膜层磨损形貌宏观上表现为由塑性变形引起的犁沟磨损,芯部发生拉伸变形,边界呈现卷曲变形。结论对Cu-AlN进行合理热处理,可改善镀层表面组织与致密度,提高结合强度和导热性能。