40Cr钢表面激光熔覆层的磨损性能

为研究模具钢熔覆层的磨损性能,采用铁基粉在40Cr钢表面进行激光熔覆,以激光熔覆层为上试样,GCr15钢珠为下试样,采用HT－500磨损试验机进行摩擦磨损试验,并与40Cr基体的磨损性能相对比。利用表面形貌仪测量磨痕深度和宽度。研究结果表明：载荷小于250 g时,相同载荷下基体的摩擦系数大。载荷小于300 g时,随磨损时间延长,熔覆层、基体的摩擦系数都随着载荷增加而减小。当载荷为300 g时,基体的摩擦系数在0.563～0.589之间变化,平均值为0.576,且随时间逐渐升高,耐磨性变差;熔覆层的磨擦系数在0.431～0.457之间变化,平均摩擦系数为0.444,磨痕深度和宽度分别是0.65 mm和1.096 μm,且随时间逐渐下降,表现了良好的耐磨性能。当载荷增加到500 g时,平均摩擦系数和磨痕深度比300 g时分别增加了75％和47倍,且摩擦系数逐渐升高,磨损性能下降。     

铁基合金激光熔覆层的高温磨损性能

 为提高40Cr钢表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备Fe基涂层,利用HT-500摩擦磨损实验机测定干摩擦条件下,基体和熔覆层的摩擦因数随温度变化的规律。利用表面粗糙度轮廓仪测量磨痕的深度和宽度,SEM观察熔覆层以及磨痕的显微组织形貌,使用HV-1000型显微硬度仪检测基体和熔覆层结合部分的硬度。研究结果表明:熔覆层平均显微硬度值达到373.8HV(0.2);显著高于基体硬度198.4HV(0.2)。在干摩擦条件下,随着温度升高,磨损过程逐渐变平缓,平均摩擦因数降低,磨损率增加,耐磨性下降;在350~400 ℃之间,熔覆层磨损性能优于基体。     

铁基合金激光熔覆层的高温磨损性能

为提高40Cr钢表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备Fe基涂层,利用HT-500摩擦磨损实验机测定干摩擦条件下,基体和熔覆层的摩擦因数随温度变化的规律。利用表面粗糙度轮廓仪测量磨痕的深度和宽度,SEM观察熔覆层以及磨痕的显微组织形貌,使用HV-1000型显微硬度仪检测基体和熔覆层结合部分的硬度。研究结果表明:熔覆层平均显微硬度值达到373.8HV(0.2);显著高于基体硬度198.4HV(0.2)。在干摩擦条件下,随着温度升高,磨损过程逐渐变平缓,平均摩擦因数降低,磨损率增加,耐磨性下降;在350~400 ℃之间,熔覆层磨损性能优于基体。     

激光熔覆NiCrBSi涂层组织及摩擦磨损性能

采用激光熔覆技术在H13钢表面制备了NiCrBSi合金涂层,利用OM,SEM,EDX和XRD等对熔覆层的微观组织进行了分析,测试了熔覆层的显微硬度和摩擦磨损性能。结果表明,激光熔覆层与基体形成了良好的冶金结合,熔覆层的组织主要由γ-Ni,Cr7C3和CrB等相组成。熔覆层显微硬度在650~850HV之间,明显高于H13钢基体的硬度。摩擦磨损实验表明,在相同的条件下,熔覆层的耐磨性比基体有了明显的提高,磨损体积减少了92.4%。通过对磨损后的试样进行粗糙度测试后表明,涂层具有更平滑的表面。     

铁基合金激光熔覆层高温润滑磨损性能

为提高40Cr合金钢的表面耐磨性,采用预置激光熔覆法在40Cr基体表面制备铁基合金涂层, 利用扫描电镜观察分析熔覆层显微组织形貌,用显微硬度仪测试熔覆层截面显微硬度,用摩擦磨损试验机测定在润滑条件下基体、熔覆层的摩擦系数随温度变化的规律。研究结果表明:熔覆层与基体实现良好冶金结合,熔覆层横截面微观组织呈现平面晶、树枝晶和胞状晶分布;熔覆层硬度值介于617.5~926.6 HV0.2之间,基体硬度介于205.2~278.2 HV0.2之间;在200 ℃以下,熔覆层摩擦系数在磨程中趋于平稳,在0.1附近轻微波动,小于基体平均摩擦系数;当温度超过200 ℃,油膜分解,引发润滑失效,磨损方式向干摩擦转化,磨损机理从微切削磨损主导向粘着磨损、磨粒磨损和氧化磨损复合磨损方式转化。     

激光熔覆TiC陶瓷涂层的组织和摩擦磨损性能研究

采用激光熔覆技术在TC4合金表面上制备了TiC陶瓷涂层,分析了熔覆层的微观组织,测试了熔覆层的硬度和摩擦磨损性能。结果表明:TiC激光熔覆层分为熔覆区和稀释区两个区域,熔覆区未受到基底的稀释,由TiC颗粒和TiC树枝晶组成;稀释区受到了基底的稀释,由TiC树枝晶和钛合金组成;TiC激光熔覆层的显微硬度在HV700~1500之间,明显地改善了TC4合金表面的摩擦和磨损性能。     

耐酸不锈钢表面激光熔覆层耐腐蚀研究

本文研究了在耐酸不锈钢基体上采用激光熔覆和等离子喷焊二种工艺形成的涂层对耐腐蚀性的影响。使用５ｋＷ横流ＣＯ２激光器对预置在基体上的Ｃｏ基自熔合金粉末进行熔覆加工,得到的熔层与等离子焊层对比：激光熔层缺陷率低,被机体稀释率更小,成品率更高。其组织致密均匀,晶粒细小,熔层硬度与强韧性更高。性能试验证明：激光熔层有更好的耐腐蚀性能。     

不锈钢表面激光熔覆层与喷焊层耐磨性对比研究

本文研究在１Ｃｒ１８Ｎｉ９Ｔｉ基体上采用激光熔覆和离子喷焊二种工艺形成的涂层对耐磨性的影响。使用５ｋＷ横流ＣＯ２激光器对预置在基体上的Ｃｏ基自熔合金粉末进行单道或多道扫描，得到的熔层与等离子焊层对比结果是：激光熔层缺陷率低，成品率高，其结构致密均匀，晶粒细小，成分稀释率更小，对基体热影响小，熔层硬度与强韧性更高。性能试验证明：激光熔层具有更高的抗擦伤磨损和抗冲击滑动高温磨损性能，耐磨性提高了一倍左右。     

基于深度学习的激光熔覆层表面气孔识别研究

为了解决熔覆层表面气孔识别技术中耗时且准确度不足的问题,文章利用深度学习技术中的语义分割网络提出了基于U-net神经网络识别熔覆层表面气孔的2BNC-Unet神经网络。通过引入Batch Normalization层以及串联注意力机制(CBAM)合理部署在神经网络中,选取交并比(IoU)与Dice系数作为网络的评价指标。研究结果表明：在测试集中,2BNC-Unet网络的交并比与Dice系数分别为86.96%、86.42%,相比U-net神经网络分别提高了7.65%、4.73%。同时为了验证该网络的性能,选用SegNet、2BNC-Unet与U-net神经网络进行对比实验,结果表明2BNC-Unet的分割效果不仅优于SegNet和U-net网络,而且熔覆层表面的气孔细节能够被完整地分割。在深度学习技术中2BNC-Unet的分割速度和准确度都有了显著地提高,气孔的分割为熔覆层的性能分析提供了帮助。     

Cr对TiC-VC增强铁基熔覆层耐蚀性及耐磨性的影响

通过X射线衍射、扫描电子显微镜、能谱仪、极化曲线和磨粒磨损实验分析,研究了不同Cr加入量对TiC-VC增强铁基激光熔覆层耐蚀性和耐磨性能的影响。结果表明:熔覆层中物相主要为α-Fe,TiC,VC和TiVC2。随着Cr加入量的增加,伴随有残余奥氏体及Cr3C2的出现,且Cr3C2呈长条状部分聚集、部分单独分布。熔覆层的耐蚀性与耐磨性随Cr加入量的增加呈现先增加后降低的趋势。熔覆粉末中加入适量的Cr元素能显著提高熔覆层的硬度与耐蚀性。当添加质量分数为3.0%的Cr时,熔覆层硬度高达1090HV0.2,且相同磨损条件下熔覆层磨损失重仅约为Q235钢的1/26;当添加质量分数为9.0%的Cr时,所得熔覆层的耐蚀性最好,约为不添加Cr时的3.26倍。     

Broad-beam laser cladding of Al-Cu alloy coating on AZ91HP magnesium alloy

The resistance to wear and corrosion of AZ91HP Mg alloy was improved by laser cladding Al-Cu alloy. It was found that the clad layer was characterized by AlCu₄ and Mg₁₇Al₁₂ grains embedded in a AlMg matrix. The bonding zone exhibited a white-light planar crystal band with thickness of 10-13 μm. The heat-affected zone formed a eutectic structure due to the Mg diffusion. The microhardness and wear resistance of the coating were improved due to the formation of the hard phases AlCu₄ and Mg₁₇Al₁₂. Owing to the formation of dense Al₂O₃ oxide film, the coating exhibited better corrosion resistance in 3.5 wt.% NaCl solution.     

Composition design and laser cladding of Ni-Zr-Al alloy coating on the magnesium surface

The cluster line criterion was used for optimized design of a Ni-Zr-Al alloy used as coating on the AZ91HP magnesium alloy by laser cladding. Results show that the coating mainly consists of an amorphous, two ternary intermetallic phases with Ni₁₀Zr₇ and Ni₂₁Zr₈ type structures resulting in high hardness, good wear resistance and corrosion resistance. The interface between the clad layer and the substrate has good metallurgical bond.     

A study of TiB2/TiB gradient coating by laser cladding on titanium alloy

TiB₂/TiB gradient coating has been fabricated by a laser cladding technique on the surface of a Ti–6Al–4V substrate using TiB₂ powder as the cladding material. The microstructure and mechanical properties of the gradient coating were analyzed by SEM, EPMA, XRD, TEM and an instrument to measure hardness. With the increasing distance from the coating surface, the content of TiB₂ particles gradually decreased, but the content of TiB short fibers gradually increased. Meanwhile, the micro-hardness and the elastic modulus of the TiB₂/TiB coating showed a gradient decreasing trend, but the fracture toughness showed a gradient increasing trend. The fracture toughness of the TiB₂/TiB coating between the center and the bottom was improved, primarily due to the debonding of TiB₂ particles and the high fracture of TiB short fibers, and the fracture position of TiB short fiber can be moved to an adjacent position. However, the debonding of TiB₂ particles was difficult to achieve at the surface of the TiB₂/TiB coating.     

Microstructure evolution of Fe-based WC composite coating prepared by laser induction hybrid rapid cladding

Fe + 50 wt.% WC composite coating was prepared by laser induction hybrid rapid cladding (LIHRC) on steel substrate. The phase and microstructure of the composite coating were investigated by X-ray diffraction (XRD), environmental scanning electron microscope (ESEM) and energy dispersive spectrum (EDS). The results showed that WC particles were dissolved almost completely to precipitate the coarse herringbone M₆C eutectic carbides and the fine dendritic M₆C carbides, and that the partially dissolved WC particles with an alloyed reaction layer were occasionally observed in the whole coating. The phases of the composite coating were composed of supersaturated solid solution α-Fe, retained austenite, Fe₃C, W₂C, M₆C and M₇C₃. The microstructure evolution in the composite coating was represented by the transformation of three parts such as Fe-based metallic matrix, dispersed carbides and incompletely dissolved WC particles. The microhardness of Fe-based WC composite coating was three times much higher than that of the substrate, but was relatively lower than that of Ni-based WC composite coating by LIHRC.     

Microstructure and properties of 6FeNiCoSiCrAlTi high-entropy alloy coating prepared by laser cladding

The content of each constituent element in the newly developed high-entropy alloys (HEAs) is always restricted in equimolar or near-equimolar ratio in order to avoid the formation of complex brittle phases during the solidification process. In this study, a 6FeNiCoSiCrAlTi high-entropy alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel substrate. The microstructure, hardness and magnetic properties have been investigated. The experimental results show that the tendency of component segregation in the conventional solidification microstructure of multi-component alloy is effectively relieved. The microstructure of the coating is mainly composed of equiaxed polygonal grains, discontinuous interdendritic segregation and nano-precipitates. EBSD observation confirms that the polygonal grains and interdendritic segregation have similar BCC structure with lots of low angle grain boundaries at the interface. The microhardness of the coating reaches 780 HV_0.5, which is much higher than most of the HEAs prepared by other methods. In addition, the coating shows excellent soft magnetic properties.     

Toughening of Fe-based laser-clad alloy coating

An investigation is reported on crack-free laser clad Fe-based alloy by use of biaxial powder feeding shielded with argon gas. The microstructure and phase structure of the coating were studied, and mechanical properties were analyzed through hardness, tension strength and wear resistance of the coating. Microstructure analysis showed that there was retained austenite with spherical particles distributed therein in the interdendritic and nearby grain boundary regions. The mechanical test results showed that net-like distributed retained austenite in the interdendritic region had certain toughening effect through blunting crack-tip. Under wear condition of high sliding speed and high loading, the wear resistance of the coating with net-like retained austenite was much higher than that of the coating with some discontinuous carbide network or carbide blocks. The results showed that toughening of laser clad Fe-based alloy with high hardness over 850 HV could be achieved by modifying interdendritic phases from net-like carbide to net-like austenite with spherical particles.