激光再制造金属零件熔覆层组织及耐磨性能

采用Fe-Cr-B-Si-Mo铁基合金粉末进行激光多层熔覆,利用金相显微镜(OM),扫描电镜(SEM),显微硬度计和磨损试验机分析了熔覆层的显微组织,测试了涂层的硬度和耐磨性能.试验发现,多层熔覆层组织致密,具有快速凝固组织特征;层间形成了冶金结合,从而使整个材料在理论上没有薄弱环节.结果表明,熔覆层硬度达到760～780HV;45钢基体的体积磨损量是激光熔覆层的21.7倍;激光熔覆层具具有较好的冶金质量和耐磨性.     

H13钢表面真空粉末烧结硬质合金覆层的组织及性能

研究了真空粉末烧结法存H13钢表面上制备硬质合金覆层的组织及性能，论述了烧结T艺对覆层显微组织的影响．分析了覆层与钢基底界面形成特点、覆层的微观硬度分布及耐磨性能。结果表明，在1280～1300℃，可获得1～3mm的硬质合金覆层，覆层和钢基底通过Fe、Cr、Mo、V、W、Co、Ni相互扩散渗透产生牢固结合，硬度达到1600HV，具有良好的耐磨性。     

高频微锻造对激光熔覆层开裂行为与表面组织的影响

多频次的微米级塑性变形可导致材料表面组织与力学行为特性的变化.采用自制的高频微锻造机构对激光熔凝NiCrBSi合金层进行了微锻造处理.利用OM研究了微锻造激光熔覆层产生的塑性变形的几何特性;利用OM,SEM观察了微锻造对激光熔凝层表面组织及开裂行为的影响.结果表明,高频微锻造可在激光熔覆NiCrBSi合金层表面产生约1...     

K418合金表面激光再制造Inconel718高温合金涂层性能研究

针对K418高温合金叶轮高温、高转数工况下形变超差大,再制造成形层力学性能降低的领域研究热点,基于波形可调制脉冲激光优化工艺,再制造Inconel718高温合金成形层。采用金相显微镜、SEM、XRD、EDS、显微硬度计对该合金涂层的显微组织形貌、相结构、界面成分分布、基本力学性能进行研究。结果表明:涂层与基体间为致密的冶金结合,涂层中部为粗大的树枝晶,与激光扫描方面成30o^45o角,由涂层中部到顶部及底部,分别退化为等轴晶和胞状晶;成形层显微硬度为4100~4400 MPa,略高于基体;晶内及晶间析出少量Laves相,减少了对成形层硬脆性的影响;摩擦磨损系数较基体略有降低,但仍符合再制造要求。     

镁合金激光-氩弧复合焊再制造熔覆成形工艺优化

目的针对镁合金零部件表面损伤和体积损伤的修复问题,采用激光-氩弧复合焊修复技术,通过对工艺参数的优化,制备出组织性能良好、缺陷少的熔覆层,形成相适应的优化修复方案,为镁合金高效修复提供技术支撑。方法采用激光-氩弧复合焊技术在ZM5合金上制备熔覆层,调整送丝速度、焊接电流、焊接速度、激光功率四种工艺参数,研究工艺参数对熔覆层成形性和尺寸的影响。结果送丝速度越小,熔覆层越光滑,呈现为扁平状,且熔宽、熔深较大。当焊接电流大于105A时,激光-氩弧复合焊的强度和焊接效果最好。焊接速度对熔覆层尺寸的影响很大,随焊接速度的增加,熔覆层向细、窄、小发展。当激光功率增加到400 W时,复合焊热输入提高,熔覆层铺展性增强。结论综合熔深、熔宽、余高的离差量,为得到成形性良好、尺寸较大的熔覆层,焊接速度应为5 mm/s,送丝速度应为23 mm/s,激光功率应在400~500 W之间,焊接电流应为120~140 A。     

多冲接触载荷下不锈钢零件激光表面熔覆层组织及其失效行为

采用5kW大功率激光器在不锈钢基材上熔覆Co基合金，制取的涂层质量优于传统的电弧、火焰堆焊以及等离子喷焊工制取的涂层。对氮肥生产上甲胺泵中的进排液组合阀多冲接触表面进行激光熔覆，成功地实现了传统工艺难以完成的涂层强化工艺，上线应用证明其抗多冲接触载荷的明显增强。承受多冲接触载荷的表面强化涂层质量与强化工艺、基体和涂层材料、涂层厚度等有关。涂层厚度应根据多冲接触载荷的性质、应力大小、基体等情况来决定，太薄的涂层会造成或加剧涂层开裂、塌陷等失效行为。激光熔覆为工程中承受多冲载荷的重要零部件表面强化提供了一种更好的工艺方法。     

激光增材再制造IN939修复区显微组织与拉伸性能研究

目的 研究采用IN939粉材对镍基高温部件增材修复的可行性,获得增材修复区微观组织与性能分布规律,为燃机部件修复提供支持.方法 探索了IN939合金激光熔覆成形工艺,并进一步开展了IN939增材修复镍基合金梯形槽试验研究,分析了增材修复区显微组织结构与物相组成,研究了激光再制造过程组织变化对修复区显微硬度、拉伸性能的影...     

高温合金激光表面熔铸涂层组织与性能的研究

研究了高温铸造镍基合金ＧＨ３３激光表面熔铸镍基合金涂层的组织与性能。结果表明，基体对涂层合金的稀释较小，涂层与基体之间形成良好的冶金结合；Ｘ射线衍射分析表明，涂层基体组织为γ－Ｎｉ枝晶，枝晶间为γ－Ｎｉ、Ｍ２３（ＣＢ）６、Ｎｉ３Ｂ、Ｃｒ２Ｂ、ＣｒＢ、ＷＣ。涂层显微硬度分布均匀，涂层耐磨性能较基体高１０倍以上，通过组织与性能的综合评价，得出了激光熔铸涂层的最佳工艺参数。     

基于TD覆层处理技术的细长孔内表面覆层性能

目的 采用热扩散法碳化物覆层处理技术,研究细长孔内壁的成层厚度、覆层形貌,以及对细长孔内壁表面硬度性能的影响;探究在不同孔径和孔长条件下,采用热扩散法碳化物覆层处理技术在孔内表面形成覆层的微观形貌及形成原因。方法 采用目前使用最为广泛的碳化钒覆层配方对试样进行覆层处理,在试样内壁表面得到各组对应的碳化钒覆层;利用X粉末衍射实验(XRPD)分析处理结束后内表面的物相组成,利用光学显微镜观察形成覆层的厚度,利用扫描电子显微镜(SEM)对表面覆层的微观组织进行分析,并采用划痕法测试其结合强度,利用显微硬度计测量其表面硬度。结果 在不同孔径的孔内壁均生成了一层碳化钒覆层。3 mm孔样品的覆层厚度相对最薄(3.06 μm),6 mm孔样品的覆层厚度相对最厚(5.29 μm);在硬度测试实验中,与未进行覆层处理的原材料相比,覆层后孔内壁的硬度均得到了强化,且6 mm孔样品的强化效果相对最佳,其表面硬度达到了1 767.8HV2/15。结论 经热扩散法碳化物覆层处理技术处理后得到的内表面覆层厚度随着孔径的增加而增加,同时覆层的厚度、表面硬度等均与孔径呈正相关;随着孔长的变化,成层厚度等出现先下降后上升的趋势;所形成的碳化钒覆层均能够有效提高材料的表面硬度。     

基于焊接的多道单层再制造熔覆层组织及性能

以基于焊接的多道单层再制造熔覆层为研究对象,研究了其横截面宏观、微观组织形貌,重点分析中间道熔覆金属微观组织特点,并对熔覆层横截面整体显微硬度和道间显微硬度进行测试,对熔覆层进行不同方向拉伸试验.结果表明,多道单层再制造熔覆层除最后一道外,每道都可分为重熔区、半熔化区、完全重结晶区及不完全重结晶区;熔覆层整体硬度两侧高...     

Influences of laser powers on microstructure and properties of the coatings on the AZ91HP magnesium alloy

Al-Si alloy coatings were prepared on AZ91HP magnesium alloy by broad-beam laser cladding; the influences of the powers on the microstructure and properties of the coatings were discussed. It was found that the microstructure of the coatings at the powers of 3 and 3.5kW was characterized by Mg₂Si dendrites, and needle-like Mg₂Al₃(hcp) dispersing in the Mg₁₇Al₁₂ matrix, whereas the coating at the power of 2.5 kW was composed of the petal-like Mg₂Al₃ (fcc) as well as the needle-like Mg₂Al₃(hcp). The coating at the power of 4 kW appeared as α-Mg solid solution and Mg₂Si, Mg₁₇Al₁₂, as well as Mg₂Al₃ (hcp). The coatings with the powers of 3 and 3.5　kW exhibited higher microhardness and better wear resistance because of more Mg₂Si and Mg₁₇Al₁₂. However, the coating at the power of 2.5 kW displayed better corrosion resistance.     

Effect of power on microstructure and properties of laser cladding NiCrBSi composite coating

A laser clad NiCrBSi composite coating was fabricated on the surface of 42CrMo steel using 6?kW fibre laser. The morphology and composition of the composite coating formed under different powers were studied using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction spectroscopy. The microhardness and wear resistance were measured with a MICROMET-5103 digital microhardness tester and a MM-200 ring-block wear testing machine, respectively. The results showed that the cladding layer and the substrate have good metallurgical bonding. The microstructure nearing the fusion line is a columnar grain and that of the cladding layer is mainly a cellular grain. The main phases of the laser cladding layer are γ-Ni, (Fe,Ni), M₇C₃, M₂₃C₆ and CrB. The dilution rate of the laser cladding layer increased with the increase of laser power. The microhardness of the cladding layers decreased with the increase of laser power, and wear resistance of the cladding layer first increased and then decreased with the increase of laser power. When the laser power was 2000?W, the wear resistance of the composite coating was at its highest.     

激光再制造技术及其工业应用

针对机械装备修复技术，阐述了激光再制造技术概念及激光再制造系统构成：三维激光光束头、三维激光涂敷系统、CAD／CAM软件和控制检测系统。展示了30层连续熔敷后的组织形貌，说明组织和硬度都比较均匀，并介绍了若干激光修复工业应用实例。     

H13钢激光熔覆Co基涂层工艺优化及组织性能

采用Nd:YAG激光器在H13钢表面制备Co基合金涂层,分析扫描速度和电流强度对涂层成形质量的影响,确定最优参数。借助扫描电镜和X射线衍射仪分析了涂层组织形貌及物相组成。使用显微硬度计和摩擦磨损试验机测试了涂层截面硬度及耐磨性能。结果表明：激光熔覆扫描速度增加和电流强度降低,均可使Co基合金涂层熔高和熔宽降低,孔洞和裂纹数量减少。优化工艺参数为：扫描速度120 mm/min,电流200 A。该工艺制备涂层组织主要由细小的枝晶和共晶组成,包括γ-Co和M23C6相,涂层硬度达到610 HV0.2;耐磨性是淬火回火态H13钢的1.32倍。     

U71Mn钢表面激光熔覆Ni60-25％WC涂层工艺参数优化的研究

目的研究U71Mn钢表面激光熔覆Ni60-25%WC涂层的最佳工艺参数。方法首先通过单道单因素试验初步选取激光功率、送粉量、扫描速度和光斑直径4个工艺参数,然后进行4因素3水平的单道正交试验,以熔覆层的宽度、高度和稀释率作为判断熔覆层质量的指标,做极差分析,最后得到最优工艺参数并分析了熔覆层的显微硬度及显微组织。结果单道单因素试验及单道正交试验得到的工艺参数均为:激光功率1500 W,送粉量4 g/min,扫描速度6 mm/s,光斑直径2.2 mm。通过单道正交试验极差表分析发现,工艺参数对质量指标的影响程度不同,对熔覆层宽度的影响为扫描速度送粉量激光功率光斑直径,对熔覆层高度的影响为送粉量扫描速度光斑直径激光功率,对熔覆层稀释率的影响为送粉量光斑直径扫描速度激光功率,对比发现送粉量是熔覆层的最大影响因子。熔覆层的显微硬度最高可达到1170HV,是基体的3.7倍。结论在U71Mn钢表面激光熔覆Ni60-25%WC涂层,可以制备出光滑且紧密结合的熔覆层,且表面硬度明显提高。     

Repair welding of ductile cast iron by laser cladding process: microstructure and mechanical properties

Abstract

The aim of this research was to determine the feasibility of a newly developed process in the repair of cracked gas turbine casings made of ductile cast iron. This study investigated the microstructural characteristics, metallurgy and mechanical properties of the repair weldments produced using fibre laser cladding. Optical microscopy, scanning electron microscopy and element probe microanalysis were used to investigate the microstructure at the cladding weld interface. The mechanical properties of the cladded specimens were evaluated after laser cladding. Our results revealed that the weldability of ductile cast iron can be enhanced by performing laser surface pretreatment to sublimate graphite nodules. Microhardness at the interface of the laser cladded weldments depended largely on the range of the heat affected zone and the degree of phase complexity. Under tensile loading, failures were limited to the base metal region of the weldments. Test results demonstrate that the impact toughness of the interface between the fusion zone and the base metal can be enhanced through the application of post-cladding heat treatment.     

曲面塑料模具激光熔覆再制造快速加工路径生成方法

对于曲面塑料模具,在其表面快速生成激光熔覆加工路径非常困难。针对这种情况,直接以零件的逆向点云模型为研究对象,通过平面与点云求交得到以密集离散点表示的近似激光扫描路径,避免了反求建模的过程。以离焦量变化极限为约束条件,在路径上搜索插补点。提出利用插补点的最近点来计算插补点曲面法向矢量作为激光束姿态的近似快速算法。应用镍基自熔性合金粉对P20材质的模具零件曲面表面进行了试验。金相分析表明所形成熔覆层组织均匀、致密,缺陷稀少;熔覆层与基体之间形成冶金结合。熔覆层中部组织出现了垂直于界面生长的柱状树枝晶,而在顶部许多的柱状树枝晶发育成等轴树枝晶。熔覆层的平均显微硬度达到330~350 HV0.2。路径中段的熔覆层厚度比起始点增加了10%。     

Monel合金表面激光熔覆Ni基稀土合金空蚀性能

采用激光熔覆技术在Monel 400合金表面制备Ni基稀土合金熔覆层。利用SEM、EDS、XRD、显微硬度计及超声波金属材料空蚀仪等设备对熔覆层的组织形貌、相结构、硬度、空蚀性能及失效机制进行了系统研究。结果表明:Y_2O_3细化了熔覆层的组织,其组织主要由γ-Ni固溶体、Ni_3B和高硬度的Cr_(23)C_6和Cr_7C_3组成,熔覆层平均硬度可达9040MPa,抗空蚀性能是Monel400合金的8.7倍,熔覆层空蚀过程失效机制主要为枝晶干的冲蚀剥落,Ni基稀土合金熔覆层的细晶强化及空蚀过程中产生阻断晶界网状结构是提高其耐空蚀性能的关键。     

激光熔覆FeCrNiCoMnBx高熵合金涂层的组织结构与性能

采用激光熔覆技术制备FeCrNiCoMnB_x高熵合金涂层,研究了硼含量对激光熔覆FeCrNiCoMnB_x高熵合金涂层的组织结构、硬度和摩擦磨损性能的影响,以及硼化物中层错形成机制。结果表明:涂层均由简单fcc结构固溶体和硼化物两相组成。当硼含量x≤0.75时,生成的硼化物以(Cr,Fe)_2B相为主;而当硼含量x=1时,生成大量的(Fe,Cr)_2B相。随着硼含量的增加,涂层中的硼化物含量增加,硬度增大,耐磨性能增强。硼化物(Fe,Cr)_2B相在(110)面存在大量堆垛层错。硼化物中的层错是(Fe,Cr)_2B相通过(110)面的层错(滑移距离为1/4[111])方式而向(Cr,Fe)_2B相转变而产生。     

Fabrication and microstructure of Fe-based amorphous composite coatings by laser cladding

Fe-based amorphous composite coatings were fabricated on AISI 1045 steel by laser cladding. The results of the X-ray diffraction and transmission electron microscopy analyses show the coating is composed of an amorphous phase in majority and a nanocrystalline phase in minority. Phase composition of the coating changes along the depth of the coating. The reasonable scanning speed for fabricating an amorphous composite coating is 3 500mm/min when the laser power is 4 800W and the laser beam diameter is 2mm. If the scanning speed is lower than 3 500mm/min, the intensity of the two main diffraction peaks in X-ray diffraction patterns of the coatings decreases with the scanning speeds increasing. At the same time, a broad halo peak emerges and enlarges. High laser power and fast scanning speed are the essential conditions of amorphization. The coating exhibits high microhardness.