汽车发动机用AZ91合金的激光表面改性处理

采用预置式两步激光熔覆的方法在汽车发动机用AZ91合金表面进行了等离子喷涂+激光熔覆改性处理,通过金相、扫描电镜、XRD、硬度和极化曲线等测试手段,研究了激光熔覆Al-Si层的显微组织和耐腐蚀性能。结果表明,激光熔覆层主要由α-Al和（α-Al+β-Si）共晶组织组成;激光熔覆层的显微硬度要高于等离子喷涂层,且两种涂层的显微硬度都要高于基体合金;改性层和基体合金的耐腐蚀性能从高至低依次为：激光熔覆层>等离子喷涂层>AZ91合金。     

不同工艺制备铁基非晶复合涂层组织与性能研究

分别采用大功率光纤激光器与超音速等离子喷涂设备在45号钢基体表面制备Fe基非晶复合涂层。采用扫描电镜、显微硬度计、X射线衍射仪对熔覆层进行微观组织和成分的研究;并分析熔覆层的显微硬度和耐腐蚀性能。结果表明,激光熔覆涂层成型良好,无明显的孔隙、宏观裂纹等缺陷,熔覆层与基体之间为结合强度较高的冶金结合。超音速等离子喷涂涂层存在一定的气孔、微裂纹等缺陷,涂层与基体之间为机械结合,结合强度相对较弱。激光熔覆层组织为柱状晶、树枝晶和非晶共存组织。激光熔覆层内组织致密,且析出了Fe-Cr、(CrFe)_7C_3化合物等硬质相。超音速等离子喷涂涂层截面形貌为典型的层状结构,涂层的非晶含量明显高于激光熔覆涂层,但由于其内部的孔隙和微裂纹,使激光熔覆涂层耐腐蚀性能优于超音速等离子喷涂涂层。     

预置粉末工艺对熔覆层组织和性能的影响

探讨了激光熔覆工艺中涂覆层材料的预置工艺对熔覆层的熔覆工艺、成分、硬度分布及相结构的影响。采用SEM、EDAX,显微硬度仪、X射线衍射仪进行测定分析。研究结果表明：在基体表面采用等离子喷涂预置涂覆粉末,经过激光熔覆能够获得成分、硬度分布均匀、组织、相结构均匀和稳定性好、热疲劳寿命长的熔覆层。     

FeCrCoWCBY2O3合金激光熔覆层的性能研究

通过对FeCrCoWCBY2O3合金粉末在低碳钢表面进行激光熔覆，获得了C、B含量较高的无裂纹熔覆层，其厚度在1．0～1．5mm之间。利用XRD、SEM等分析了熔覆层的成分及显微组织结构，并测试了涂层的硬度和耐磨性。结果显示：激光处理后表面迅速熔化和冷却，组织由马氏体、残余奥氏体枝晶和枝晶间碳化物组成；熔覆层的硬度比熔覆基体提高3倍多，且硬度最高值不在表层，而在距离表面0．3mm处；耐磨性相对基体提高接近2倍。     

热锻模表面激光熔覆金属陶瓷覆层的试验研究

为了制备符合锻模使用性能要求的模膛表面强化层,进行了在指定的W6Mo5Cr4V2基体上激光熔覆金属陶瓷Ni60/Ni-Cr-Cr3C2的试验研究.主要研究熔覆材料的成分构成,熔覆时的激光参数及所制备的熔覆层的物相、组织形貌及显微硬度分布.试验结果说明,采用50%:50%的Ni60粉和Ni-Cr-Cr3C2粉做覆层材料,采用激光功率1.7 kW,扫描速度4 mm·s-1,光斑直径为3 mm,预涂厚度为0.6 mm的激光熔覆工艺,可以得到组织细化硬度较高的激光覆层.说明激光熔覆金属陶瓷是制备热锻模膛表面强化层的一种有前途的方法.     

45钢表面WC-12Co金属陶瓷激光熔覆层的组织与性能研究

采用火焰喷涂技术,在45钢表面预置一层WC-12Co并进行激光熔覆实验.SEM分析试样显微组织与形貌,EDS分析界面元素分布特性,HXD-1000B维氏显微硬度仪分析显微硬度分布特征.结果表明,经激光熔覆后,火焰喷涂层所固有的片层状组织消失,形成了较为致密的熔覆层,涂层与基体间呈现冶金结合状态;熔覆层显微组织由表及里依次呈现多边形块状、枝晶状、颗粒状.熔覆层表层硬度最高,随着深度的增加,硬度逐渐下降,熔覆层与基体界面处硬度发生突变.     

灰铸铁激光熔覆铁基和镍基粉末的比较*

采用高功率横流CO2激光器,以铁基和镍基合金粉末为熔覆材料,用同步送粉法在灰铸铁基体材料上进行激光熔覆试验,并对熔覆层组织和性能进行比较分析。结果表明,激光熔覆镍基时覆层内的组织较铁基合金熔覆层组织均匀细致;熔覆镍基和铁基粉末合金层与基体结合紧密成冶金结合;结合区的组织晶粒细小,合金碳化物含量高,其硬度也最高。用正交试验法分析激光功率、扫描速度、熔覆层数对熔覆效果、表面硬度的影响规律,获得激光熔覆层表面硬度显著提高;对表面硬度影响最大的因素是扫描速度,其次是激光功率,熔覆层数则影响不大。熔覆Fe35合金粉末综合优化参数为扫描速度300mm/min、激光功率4.0kW、熔覆二层。熔覆Ni20A合金粉末优化参数为扫描速度400mm/min、激光功率4.0kW。     

激光熔覆超音速火焰喷涂陶瓷复合涂层的结构和性能

对YAG激光器产生的矩形激光束及在熔覆超音速火焰喷涂陶瓷复合涂层过程中激光功率对涂层组织和性能的影响进行了研究.采用扫描电镜分析了激光熔覆后的涂层组织结构,比较了采用不同激光输出功率2、3、4kW所得熔覆层的显微硬度和耐磨性能.结果表明:激光熔覆层与基体为冶金结合,熔覆层的硬度较喷涂层的硬度有所提高,并随着激光功率的提高而增加.激光熔覆层的磨损失重远低于喷涂层.     

激光熔覆制备楔块高硬度层的工艺方法研究

为获得表面高硬度层及冶金结合,分别以铸铁和普通碳钢为基体,以含WC的镍基合金粉末为熔覆材料,采用激光熔覆技术制备了大面积的熔覆层。测试了熔覆层、结合处以及基体的硬度,并采用扫描电镜、能谱仪对熔覆层进行了微观组织分析。结果表明,以铸铁为基体不易制得良好的熔覆层,而以45钢为基体时,在激光功率1200~2000W之间,扫描速度在2 mm/s左右时能获得质量良好的熔覆层。熔覆层表面硬度高达1100 HV以上,熔覆层与基体呈冶金结合,熔覆层无微观裂纹,微观组织分布均匀,磨削平整后熔覆层厚度可达1 mm以上。     

层间停光时间对多层激光熔覆影响实验研究

采用Fe基合金粉末在Q235D钢表面进行多层激光熔覆实验,得到的熔覆层表面比较光滑平整、粗糙程度较小,没有宏观裂纹和气孔出现,通过金相组织观察发现熔覆层组织晶粒的尺寸比较细小,熔覆层组织较好,无裂纹,基本无气孔出现,熔覆层与基体冶金结合较好。实验分别采用不同的层间停光时间进行多层激光熔覆,结果发现:多层熔覆时当停光时间较短时,熔覆层整体的显微硬度值会随着熔覆层数的增加而有所下降,并且熔覆层硬度的变化规律为:与基体结合的第一熔覆层硬度最高,往上层依次逐级降低,最后一层的硬度最低;当停光时间较长时,熔覆层的整体显微硬度值同样也会随着熔覆层数的增加而降低,而各熔覆层变化规律有所不同的是与基体结合的第一熔覆层硬度最低,往上层依次逐级升高,最后一层的硬度最高。实验结果对实际生产有重要的研究和应用价值。     

Wear and corrosion resistance of laser remelted and plasma sprayed Ni and Cr coatings on copper

Nickel and chromium coatings were produced on the copper sheet using plasma spraying and laser remelting. The sliding wear test was achieved on a block-on-ring tester and the corrosion test was carried out in an acidic atmosphere. The corrosive behaviors of both coatings and original copper samples were investigated by using an impedance comparison method. The experimental results show that the nickel and chromium coatings display better wear resistance and corrosion resistance relative to the original pure copper sample. The wear resistance of the coatings is 8 - 12 times as large as original samples, and the wear resistance of laser remelted samples is better than that of plasma sprayed ones. The corrosion resistance of laser remelted nickel and chromium samples is better than that of plasma sprayed samples respectively. The corrosion rate of chromium coatings is less than that of nickel coatings, and the laser remelted Cr coating exhibits the least corrosion rate.     

激光重熔对Al2O3-40% TiO2等离子喷涂层耐冲蚀性能的影响

利用等离子喷涂方法制备Al₂O₃-40% TiO₂涂层,对涂层进行激光重熔处理.分别对等离子喷涂层和激光重熔涂层进行耐冲蚀磨损性能试验,研究了激光重熔对Al₂O₃-40% TiO₂等离子喷涂层耐冲蚀性能的影响.结果表明,激光重熔消除了Al₂O₃-40% TiO₂等离子喷涂层的层状结构,使得等离子喷涂层中γ-Al₂O₃转变为α-Al₂O₃,形成了α-Al₂O₃+TiAl₂O₅稳定结构.激光重熔后的涂层组织致密均匀、硬度高,具有冶金结合特征,使得耐冲蚀性能得到极大提高,其磨损特征为冲蚀粒子冲击作用下产生的裂纹、破碎与块状剥落.     

激光重熔镍镀层复合工艺制备铜合金表面涂层

在铜合金表面先预置镍镀层再激光重熔以获得界面冶金结合可靠的新涂层. 通过优化工艺参数,并利用多种分析手段研究了涂层的组织、界面结构和显微硬度. 结果表明,室温下采用4 200 W半导体激光重熔0.4 mm厚镍镀层可获得无缺陷且界面冶金结合可靠的激光熔覆涂层;所获新涂层组织均匀致密,物相由重熔前的γ-Ni镀层转变为重熔后的(Ni,Cu)固溶体;涂层硬度约为135 HV0.05,稍高于CuCrZr基体硬度. 镍镀层的预置和半导体激光的应用提高了铜基表面激光能量的吸收率;新涂层与铜基体间组织成分及硬度匹配保证了良好的界面相容性和可靠的界面结合.     

点焊电极表面电火花强化TiC-TiB2涂层

以Ti、B4C和Cu等粉末为原料,采用自蔓延高温合成工艺制备TiC-TiB2复合材料,并通过电火花表面强化在点焊镀锌钢板用电极的表面制备TiC-TiB2复合强化层。用四探针法测量了强化层的电导率,利用SEM和XRD分析了强化层的微观结构和物相,运用点焊实验测试了强化电极的使用寿命,初步分析了强化层对电极失效的影响。结果表明:电火花强化层致密无明显分层,强化层与基体间为牢固的冶金结合;强化层物相主要为TiB2、TiC、B2O3和Cu等,强化层中的非晶组织和组织细化使其衍射峰宽化;TiC-TiB2复合强化层的导电率可达86.53%IACS,具有良好的导电性能,适合制作点焊电极材料;强化电极的点焊寿命比无强化层电极大约提高了4倍。     

Some properties,inhomogeneities, and applications of plasma sprayed electroconductive Cu-based coatings

This article reports on the effects of inhomogeneities on properties of plasma sprayed electroconductive copper and CuSn coatings. These coatings, in combination with aluminum-alloy-based substrates, are of interest for applications in the power industry, particularly for the production of diverse types of power clamps and armatures for switching stations of high and very high tension electrical equipment. The properties of an aluminum alloy substrate with an electroconductive coating were examined, including coating structure, character of coating substrate boundary, strength, hardness and adhesion of the coating, as well as electrical conductivity and contact resistance between the substrate and coating.     

Corrosion behavior of HVOF-sprayed and Nd-YAG laser-remelted high-chromium,nickel-chromium coatings

Thermal spray processes are widely used to deposit high-chromium, nickel-chromium coatings to improve high temperature oxidation and corrosion behavior. However, despite the efforts made to improve the present spraying techniques, such as high-velocity oxyfuel (HVOF) and plasma spraying, these coatings may still exhibit certain defects, such as unmelted particles, oxide layers at splat boundaries, porosity, and cracks, which are detrimental to corrosion performance in severe operating conditions. Because of the process temperature, only mechanical bonding is obtained between the coating and substrate. Laser remelting of the sprayed coatings was studied in order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties. The coating material was high-chromium, nickel-chromium alloy, which contains small amounts of molybdenum and boron (53.3% Cr, 42.5% Ni, 2.5% Mo, 0.5% B). The coatings were prepared by HVOF spraying onto mild steel substrates. A high-power, fiber-coupled, continuous-wave Nd:YAG laser equipped with large beam optics was used to remelt the HVOF-sprayed coating using different levels of scanning speed and beam width (10 or 20 mm). Coating that was remelted with the highest traverse speed suffered from cracking because of the rapid solidification inherent to laser processing. However, after the appropriate laser parameters were chosen, nonporous, crack-free coatings with minimal dilution between coating and substrate were produced. Laser remelting resulted in the formation of a dense oxide layer on top of the coatings and full homogenization of the sprayed structure. The coatings as sprayed and after laser remelting were characterized by optical and electron microscopy (OM, SEM, respectively). Dilution between coating and substrate was studied with energy dispersive spectrometry (EDS). The properties of the laser-remelted coatings were directly compared with properties of as-sprayed HVOF coatings.     

冷喷涂Cu402F涂层激光重熔表面改性后摩擦学行为

目的研究激光重熔后冷喷涂Cu402F涂层在腐蚀介质中的摩擦学行为。方法采用冷喷涂技术在镍铝青铜9442合金上制备了厚度约为882.11μm的Cu402F涂层,并使用激光重熔技术对冷喷涂涂层进行表面改性。使用OM、SEM观察涂层截面与表面的微观形貌;使用XRD、X射线残余应力测试仪、多功能表面性能测试仪、多频直线往复磨蚀实验机,重点表征测试了涂层的组织、表面残余应力、摩擦学性能与磨蚀行为。结果激光重熔后的涂层分为表面重熔层、多孔的重熔过渡层以及冷喷涂遗传层。激光重熔前后,涂层的物相、残余应力均未发生较大变化。在20、50、100 N条件下,激光重熔态涂层的平均摩擦系数呈递增趋势,磨损率分别为1.01×10~(-2)、1.17×10~(-2)、1.34×10~(-2) mm~3/(N·m);由磨蚀实验可知,磨蚀是涂层表面产生钝化膜与钝化膜被破坏的此消彼长的过程,反映着摩擦与腐蚀的协同作用,涂层在磨蚀过程中,开路电位与摩擦系数呈正相关,说明激光重熔态涂层表面钝化膜产生的速度快于钝化膜被坏的速度。结论激光重熔保留了冷喷涂技术制备的Cu402F涂层的优点,同时激光重熔涂层上产生钝化膜的速度更快,有利于提高涂层的耐磨蚀性能。     

等离子喷涂-重熔NiCrBSi涂层的显微组织与耐磨性能

采用等离子喷涂和等离子重熔技术,在2Cr13基体表面制备2mm厚的自熔性NiCrBSi涂层。利用扫描电镜、X射线衍射仪和能谱仪研究涂层形貌、微观组织和微区成分的演变规律,采用拉伸和硬度试验测试涂层的结合强度和显微硬度,通过室温和高温摩擦磨损试验评价和比较涂层与基体的耐磨性能。结果表明,重熔前后涂层都是由γ-Ni固溶体以及Ni₃B,CrB,Cr₂B,Cr₇C₃和Cr₂₃C₆等组成;重熔涂层由层状喷涂态转变为致密的铸造态,涂层组织和力学性能大大提高,结合强度和显微硬度分别高达200MPa和1010HV。重熔涂层的耐磨性显著优于2Cr13基体,其600℃时的磨损体积仅为基体的20%。     

等离子喷涂ZrO2层经激光再熔后的组织变化

本文研究了等离子喷涂ZrO_2陶瓷层的激光再熔化处理经激光再熔化处理的ZrO_2涂层致密、无孔隙,但熔化层有裂纹在ZrO_2中添加适量的SiO_2,降低了熔化层在冷却时的热应力,有效抑制裂纹的产生经激光再熔化处理后的陶瓷展和粘结层之间的结合为冶金结合;粘结尾和基材的冶金结合层厚度明显增加;随着激光功率的增加,陶瓷层、粘结层以及一定厚度的基材发生熔化,陶瓷层和粘结层之间产生Zr_6Fe_3O反应相