【作者】 姜洋；

【导师】 张鑫龙；

【作者基本信息】 东北林业大学 ， 机械工程， 2025， 硕士

【摘要】 激光熔覆技术因其简便的工艺流程和高效的材料利用率而被视为一种先进的表面改进技术。高熵合金是近些年新兴起的一种特殊合金材料,它的出现是对传统合金材料领域的一次重要革新。由于Q235钢具有良好的焊接性能和塑性,价格低廉,被广泛应用于车辆、船舶、桥梁等制造行业。但硬度低、耐磨性差、不耐腐蚀等特性阻碍了其发展,因此改善其表面性能是提升整体性能和范围应用的关键所在。本文的研究聚焦于单因素条件下,系统地探索不同工艺参数对单道Fe Co Ni Cr Mn涂层的宏观形貌、截面几何尺寸、微观组织及性能的影响。此外,研究不同搭接率对多道Fe Co Ni Cr Mn涂层成型质量的影响,并对涂层界面的结合形态进行表征。测试涂层的显微硬度、耐磨性及耐腐蚀性等关键性能,以评估其在实际应用中的潜力和可行性。研究激光工艺参数对单道涂层成形的影响规律。发现激光功率在1.0 k W～2.0 k W、扫描速度在300 mm/min～800 mm/min、送粉速率在6 g/min～12 g/min区间内的单道熔覆涂层表面无气孔、裂纹、起球等缺陷,并与基材结合良好。随着激光功率的增加,涂层的深度、宽度以及基材的稀释率均呈上升趋势;随着扫描速度的增加,熔池的宽度和高度均有所降低;随着送粉速率的增加,熔池的深度及基材稀释率逐渐减少,而熔池的高度和宽度则逐渐增加。深入分析涂层的相结构特征、微观组织形态、元素分布状况,并测定了其显微硬度及耐磨性能。熔覆涂层的主要为单一的FCC相结构,不随参数的变化而改变;显微组织为典型的柱状晶和等轴晶组织,并随着激光功率、扫描速度和送粉速率的增加,熔覆涂层内的柱状晶逐渐向等轴晶转变。不同工艺参数所制备的熔覆涂层硬度均高于基材,尤其是熔覆涂层热影响区的硬度远高于和基材,最高可达488.5 HV,显著地改善了基材表面的硬度。在相同的摩擦磨损条件下,各参数熔覆涂层的磨损量和磨痕宽度均小于基材,摩擦系数由基材的0.535最低降至0.311。熔覆涂层磨损方式为磨粒磨损为主,磨痕面较为平整,耐磨性显著提高,与显微硬度成正比。在单道激光熔覆的基础上,制备不同搭接率的多道激光熔覆涂层,并对性能进行表征。50%搭接率熔覆涂层的表面质量良好且综合性能表现最佳,第一道熔覆涂层为第二道熔覆提供了界面模板,引导柱状晶在冷却过程中倾向于沿垂直于界面的方向生长,随着搭接率的提升,非搭接区内的柱状晶数量逐渐减少。其中,显微硬度及耐磨性对基材都有显著提升,相较于单道激光熔覆,多道激光熔覆的热影响区硬度显著降低,随着搭接率的提高,显微硬度逐渐增大,非搭接区的硬度高于搭接区;自腐蚀电流密度为2.27×10^-6 A·cm^-2,约是基材的1/2,同时较基材电阻增加了2.1倍。更多还原

【Abstract】 Laser cladding technology is regarded as an advanced surface improvement technology due to its easy process flow and efficient material utilization.High-entropy alloy is a newly emerging special alloy material in recent years,and its appearance is an important innovation in the field of traditional alloy materials.Due to its good welding performance and plasticity,Q235 steel is inexpensive and is widely used in vehicle,ship,bridge and other manufacturing industries.However,properties such as low hardness,poor wear resistance,and non-corrosion resistance hinder its development,so improving its surface properties is the key to enhance the overall performance and range of applications.The study in this thesis focuses on single-factor conditions to systematically explore the effects of different process parameters on the macroscopic morphology,cross-sectional geometry,microstructure and properties of single-pass Fe Co Ni Cr Mn coatings.In addition,the effects of different lap rates on the molding quality of multi-pass Fe Co Ni Cr Mn coatings are investigated and the bonding morphology at the coating interface is characterized.The key properties of the coatings,such as microhardness,wear resistance and corrosion resistance,are tested to assess their potential and feasibility in practical applications.The influence law of laser process parameters on single-pass coating molding was investigated.It was found that the surface of single-pass molten coating with laser power of 1.0 k W～2.0 k W,scanning speed of300 mm/min～800 mm/min,and powder feeding rate of 6 g/min～12 g/min had no defects such as porosity,cracks,and balling,and was well bonded with the base material.With the increase of laser power,the depth and width of the coating as well as the dilution rate of the substrate showed an increasing trend;with the increase of scanning speed,the width and height of the molten pool decreased;with the increase of powder feeding rate,the depth of the molten pool and the dilution rate of the substrate gradually decreased,while the height and width of the molten pool gradually increased.In-depth analysis of the phase structure characteristics,microstructure morphology,element distribution status of the coating,and determination of its microhardness and wear resistance.The main phase structure of the fusion-coated coating is a single FCC phase structure,which does not change with the change of parameters;the microstructure is a typical columnar and equiaxial crystal organization,and with the increase of laser power,scanning speed and powder feeding rate,the columnar crystals within the fusion-coated coating are gradually transformed to equiaxial crystals.The hardness of the fused coating prepared by different process parameters is higher than that of the substrate,especially the hardness of the heat-affected zone of the fused coating is much higher than that of the substrate,which can reach up to 488.5 HV,and the hardness of the surface of the substrate is significantly improved.Under the same friction and wear conditions,the abrasion amount and the width of abrasion marks of the fusion-coated coatings were smaller than those of the substrate,and the friction coefficient was reduced from 0.535 to 0.311,and the wear mode of the fusion-coated coatings was dominated by abrasive abrasion,with the abrasion mark surface being flatter and the abrasion resistance being significantly improved,which was directly proportional to the microhardness.On the basis of single-pass laser cladding,multi-pass laser cladding coatings with different lap rates were prepared and characterized.50%lap rate cladding coatings showed good surface quality and the best overall performance,and the first-pass cladding coatings provided an interfacial template for the second-pass cladding coatings,which guided the growth of columnar crystals in the direction perpendicular to the interface during the cooling process,and the number of columnar crystals in the non-lap region gradually decreased with the increase of the lap rate.As the lap rate increases,the number of columnar crystals in the non-lap zone gradually decreases.Among them,the microhardness and abrasion resistance of the substrate were significantly improved.Compared with the single-pass laser cladding,the hardness of the heat-affected zone of the multi-pass laser cladding was significantly reduced,and the microhardness gradually increased with the increase of the lap rate,and the hardness of the non-lapped zone was higher than that of the lapped zone;the self-corrosion current density of the coating was 2.27×10^-6 A·cm^-2,which is about 1/2 that of the substrate,and at the same time,the resistance of the coating was increased by a factor of 2.1 compared with that of the substrate.更多还原