TiC含量对激光熔覆AlCoCrFeNi基高熵合金复合涂层抗磨损和耐腐蚀性能的影响

Influence of TiC Content on Wear&Corrosion Resistance of AlCoCrFeNi-Based High-Entropy Alloy Composite Coatings Fabricated by Laser Cladding

通过激光熔覆在2205双相不锈钢表面制备了TiC增强AlCoCrFeNi基高熵合金复合涂层。通过X射线衍射仪、场发射扫描电子显微镜表征了AlCoCrFeNi+TiC熔覆层的物相组成和微观形貌,采用维氏硬度计测定了熔覆层的显微硬度,利用线性往复式摩擦磨损试验机测试了熔覆层的抗磨损性能,通过电化学工作站测试了熔覆层的耐腐蚀性能。结果表明:TiC增强AlCoCrFeNi基熔覆层主要由BCC相和TiC相组成。随着TiC添加量的增加,TiC相的相对含量逐渐提高而BCC相含量逐渐下降。熔覆层的显微组织由等轴晶基体和第二相组成,基体晶粒尺寸随着TiC含量的增加而逐渐减小。随着TiC含量的增加,由于弥散强化效应熔覆层的显微硬度逐渐提高,而抗磨损性能先提高后降低。过量TiC导致第二相团聚和组织缺陷的产生,从而导致熔覆层的致密性降低,抗磨损性能下降。熔覆层的磨损机制主要为磨粒磨损。熔覆层的耐腐蚀性能随着TiC含量的增加先提高后逐渐降低,这是由于少量TiC溶解产生的Ti能够提高熔覆层的钝化膜形成能力,而过量的TiC会增强电偶腐蚀效应。

TiC-strengthened AlCoCrFeNi-based high-entropy alloy composite coatings were fabricated on the surface of 2255 DSS by laser cladding.The phase composition and micromorphology of AlCoCrFeNi+TiC cladding layers were characterized by X-ray diffractometer and field emission scanning electron micro-scope.The microhardness of the cladding layer was measured by Vickers hardness tester,the wear resis-tance was tested by linear reciprocating friction and wear tester,and the corrosion resistance was tested in an electrochemical workstation.The results show that TiC-strengthened AlCoCrFeNi-based cladding layers mainly consist of BCC phase and TiC phase.As the TiC addition increases,the relative content of TiC phase gradually increases and that of BCC phase gradually decreases.The microstructure of the cladding layer is composed of equiaxed crystal matrix and the second phase,and the matrix grains are gradually refined with the increase of TiC content.With the rising content of TiC,the microhardness of the cladding layer gradu-ally grows due to the dispersion strengthening effect,while the wear resistance first increases and then de-clines.Excessive TiC results in the agglomeration of the second phase and the formation of microstructure defects,which leads to the decrease of the compactness and wear resistance of the cladding layer.The wear mechanism of cladding layers is mainly abrasive wear.As the TiC content rises,the corrosion resistance first increases and then gradually decreases.This is because Ti produced by the dissolution of a small amount of TiC can improve the passivation film formation ability of the cladding layer,while excessive TiC can enhance the galvanic couple corrosion effect.