摘要
为拓展304奥氏体不锈钢的使用范围,探究了激光定向沉积工艺对Inconel 718/304奥氏体不锈钢连接件组织和力学性能的影响,获得了改善上述两种合金连接工艺和质量的理论依据。利用激光沉积工艺制备Inconel 718/304不锈钢连接件,基于高速红外测温计对沉积件的热累积效应进行原位观察分析,基于组织观察明确了激光沉积热行为对Inconel 718沉积层、Inconel 718/304不锈钢界面以及基体组织的影响,揭示了组织变化对沉积件各区域显微硬度分布的影响,最后比较了异种金属连接件和304不锈钢制件力学性能的差异。研究结果表明:在热累积效应作用下,沉积件自身温度升高,热耗散减少,冷却速率降低,Inconel 718沉积层内的晶粒多以柱状晶和胞状晶形式存在;受敏化温度的影响,C、Cr等元素在304不锈钢界面熔合区和高温热影响区内偏析形成第二硬质相M_(23)C_(6),这两个区域的平均硬度分别高达251 HV0.1和238 HV0.1,显著高于母材(220 HV0.1);Inconel 718/304异种金属连接件具有较好的延展性,其平均伸长率约为53.9%,平均屈服强度相比304不锈钢提升了5.4%。短时效激光沉积工艺能较好地实现Inconel 718/304异种金属的连接,析出的少量M_(23)C_(6)硬质强化相使得该异种金属制件的抗拉强度和显微硬度较304不锈钢制件均有所提升。
Objective Austenitic stainless steel is widely utilized in modern manufacturing due to its excellent corrosion resistance and ease of processing.However,it exhibits relatively low deformation resistance and poor hardness as well as wear resistance.Inconel 718,an alloy with superior mechanical properties and excellent corrosion resistance,is employed in laser directional energy deposition(LDED)to enable additive manufacturing of dissimilar metals.To improve the connection process and quality of the two materials as well as expand the application of LDED for joining Inconel 718 alloy with 304 stainless steel,it is essential to investigate the influence of the laser deposition thermal cycle on the microstructure evolution of Inconel 718/304 connectors.This study also seeks to clarify the changes in mechanical properties resulting from the microstructure evolution.Methods 304 stainless steel was selected as the substrate,and Inconel 718 alloy powder(particle size:53‒150μm)was used as the cladding deposition material.The laser heat source was generated using an IPGYLS6000 fiber laser(maximum power:6 kW,wavelength:1070 nm,spot diameter:3 mm),with a volume fraction of 99.99%argon as the shielding gas.A reciprocating layerbylayer deposition process model was constructed using the KUKA industrial robot KRL programming system.The thermal cycle temperature of the deposited parts was dynamically monitored using an infrared pyrometer.Specimens were prepared via wire cutting,and their microstructure,composition,microhardness,and tensile property were analyzed using a scanning electron microscope,Xray diffractometer,microhardness tester,and universal testing machine to explore the effects of thermal cycling temperature on the mechanical properties of the components.Results and Discussions Inconel 718/304 connectors were successfully fabricated using LDED technology,and their microstructure and mechanical properties were analyzed.The results revealed the following:(1)Due to the heat accumulation effect,heat dissipation in the deposited part is reduced,leading to increased temperatures,decreased cooling rates,and gradual coarsening of Inconel 718 dendrites from the bottom to the top.Under the combined influence of the temperature gradient(G)and solidification rate(R),dendrites predominantly appear as columnar and cellular crystals.(2)The Inconel 718/304 macro interface is clearly defined.Delta hightemperature ferrite precipitates on the austenite crystal surface in the interface remelting zone,and M23C6 secondary hard phase disperses in the heataffected zone.The microhardness of each zone is as follows:Inconel 718 deposition layer>heataffected zone>base metal.The average microhardness values of the abovementioned areas are 283,238,and 220 HV0.1,respectively.(3)Due to precipitation carbide dispersion strengthening,the average yield strength of Inconel 718/304 parts is higher than that of hotrolled 304 stainless steel parts,reaching 376.0 MPa.The tensile strengths of the two parts are similar,at 720.0 MPa and 716.7 MPa,respectively.The overall elongation of the Inconel 718/304 parts is 53.9%,and their fracture mode exhibits mixed characteristics.Conclusions The shorttime laser deposition process effectively facilitates the connection of Inconel 718/304 dissimilar metals.By precipitating a small amount of M23C6 hardstrengthening phase,the tensile properties and microhardness of the connectors are significantly improved compared to 304 stainless steel components.
作者
吴军
张元祥
朱冬冬
李董航
余建平
Wu Jun;Zhang Yuanxiang;Zhu Dongdong;Li Donghang;Yu Jianping(Department of Mechanical Engineering,Quzhou University,Quzhou 324000,Zhejiang,China)
出处
《中国激光》
北大核心
2025年第8期221-232,共12页
Chinese Journal of Lasers
基金
浙江省自然科学基金(LTGC23E050001)。
