激光能量密度对FCC+BCC双相共晶高熵合金磨损性能与力学性能影响的研究

Effect of Laser Energy Density on Wear and Mechanical Properties of FCC+BCC Dual-Phase Eutectic High Entropy Alloy

摘要:

高熵合金通常倾向于形成单一的FCC和BCC相，导致其在强度和塑性方面兼容性较差，在复杂工况下服役寿命显著降低。然而，AlCoCrFeNi_2.1双相共晶高熵合金因具有独特的软硬交替的片层状结构，在实现良好的强韧性匹配方面有着巨大潜力，被广泛地应用于航空航天、核电、深海等领域。激光熔覆（La-ser cladding，LC）技术用于材料表面改性和零部件成形，该技术利用高能激光束将基材表面的粉末迅速熔化粘结，从而形成具有冶金结合的涂层。LC工艺参数的选择对涂层的成形质量及性能有着重要影响，其中激光能量密度作为激光功率、扫描速度和光斑直径的综合参数，对于工艺调控尤为关键。采用LC技术，在以38CrMoAl作为基体、氩气和氦气作为保护气的前提条件下，制备了FCC+BCC双相AlCoCrFeNi_2.1双相共晶高熵合金复合涂层，并对激光能量密度与涂层成形质量、显微硬度、显微硬度、磨损性能和压缩性能展开了探究。结果表明，由于Al元素的熔点与其他元素存在差异，因此涂层存在少量的孔隙，但无裂纹等缺陷。随着激光能量密度的升高，涂层显微硬度表现出先降低后上升的趋势。当激光能量为45 J?mm^-2时，涂层平均显微硬度值最大为315.2 HV_0.2，同时涂层磨损性能也表现最优，磨损体积及磨损率分别为0.508 mm³和1.686×10^-4 mm³?N^-1?m^-1，磨损机制主要为磨粒磨损和粘着磨损。随着激光能量密度的增加，AlCoCrFeNi_2.1高熵合金涂层的变形量和抗压性能逐渐增强。磨损性能与压缩性能的差异，主要归因于AlCoCrFeNi_2.1双相共晶高熵合金涂层是由较软的FCC相和较硬的BCC相组成，从而形成独特的层片状双相共晶结构，在提高塑性的同时保持了一定的强度。

Abstract:

The AlCoCrFeNi_2.1 dual-phase eutectic high-entropy alloy （EHEA） demonstrates significant potential for achieving an excellent balance of strength and toughness due to its unique lamellar structure， which alternates between soft and hard phases. This alloy is widely used in aerospace， nuclear power， deep-sea exploration， and other advanced fields. In this study， AlCoCrFeNi_2.1 dual-phase EHEA coatings were prepared using laser cladding technology by adjusting different laser energy densities. The results indicate that， due to the melting point difference of the Al element， the coatings contain a small number of pores but no cracks or other defects. As the laser energy density increases， the microhardness of the coating initially decreases before rising again， with optimal performance achieved at a laser energy density of 45 J?mm^-2， where the average microhardness reaches 315.2 HV_0.2. Additionally， wear resistance is maximized at this energy density， exhibiting a wear volume of 0.508 mm3 and a wear rate of 1.686×10?? mm3?N^-1?m^-1. The main wear mechanisms are identified as abrasive wear and adhesive wear. As the laser energy density increases， the deformation of the AlCoCrFeNi_2.1 EHEA coating and its compressive strength improve. The differences in wear resistance and compressive strength are primarily attributed to the unique lamellar structure of alternating phases in the AlCoCrFeNi_2.1 dual-phase EHEA coating， which consists of a softer FCC （face-centered cubic） phase and a harder BCC （body-centered cubic） phase， effectively enhancing plasticity while maintaining a considerable level of strength.