Microstructure and mechanical properties of ultra-high strength AerMet 100 Steel formed by laser metal deposition
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摘要:
采用正交试验制备了激光直接沉积成形(laser metal deposition, LMD)AerMet100高强钢,借助光学显微镜、扫描电子显微镜、电子探针、显微硬度仪、室温拉伸及冲击试验对制备的合金显微组织和力学性能进行了研究. 结果表明,激光沉积成形AerMet100高强钢的优化热输入区间为170 ~ 250 J/mm;沉积组织为沿凝固方向的由板条状马氏体与胞状枝晶边界的残余奥氏体组成的柱状胞晶,板条状马氏体由奥氏体在激光成形过程的快速冷却形成,而残余奥氏体主要由于凝固过程中奥氏体稳定化元素Cr、Mo、Ni元素偏析形成;沉积态硬度与基材硬度相当,但由于沉积过程中的热量累积促使基体中的回火马氏体发生高温回火,使得在沉积方向上存在明显的热影响区(heat affected zone, HAZ)软化;通过工艺优化激光沉积成形AerMet100高强钢在P =
1700 W,vs = 10 mm/s时获得较优异的综合力学性能,抗拉强度、屈服强度分别达1865.3 、1585.5 MPa,断后伸长率达12.4%. 通过断口形貌分析,随着热输入密度的降低,拉伸断口剪切唇消失,韧窝深度变浅;冲击断口解理面增大,由韧性断裂转变为脆性断裂.-
关键词:
- 激光直接沉积 /
- AerMet100高强钢 /
- 显微组织 /
- 力学性能
Abstract:Orthogonal experiments were conducted to fabricate AerMet100 high-strength steel via laser metal deposition (LMD). The microstructure and mechanical properties of the deposited alloy were systematically investigated using optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), microhardness testing, room-temperature tensile testing, and impact testing. Results indicate that the optimal linear energy density range for LMD-processed AerMet100 steel is 170 ~ 250 J/mm. The deposited microstructure consists of columnar cellular crystals containing lath martensite along the solidification direction and residual austenite at cellular dendrite boundaries. The lath martensite forms through rapid cooling-induced austenite transformation during laser processing, while the residual austenite primarily results from the segregation of austenite-stabilizing elements (Cr, Mo, Ni) during solidification. The hardness of the as-deposited matches that of the matrix, but heat accumulation during deposition induces high-temperature tempering of the matrix's tempered martensite, creating significant heat-affected zone (HAZ) softening along the deposition direction. Process optimization enabled the laser-deposited AerMet100 high-strength steel to achieve superior comprehensive mechanical properties at laser power P = 1700 W and scanning speed Vs = 10 mm/s, demonstrating ultimate tensile strength of 1 865.3 MPa, yield strength of 1 585.5 MPa, and elongation of 12.4%. Fracture morphology analysis reveals that decreasing linear energy density eliminates shear lips on tensile fracture surfaces, reduces dimple depth, increases cleavage facets on impact fracture surfaces, and shifts fracture mode from ductile to brittle.
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表 1 AerMet100钢粉末化学成分(质量分数,%)
Table 1 Chemical compositions of AerMet100 alloy steel
C Co Ni Cr Mo Si Mn Al Ti Fe 0.21 ~ 0.25 13.0 ~ 14.0 11.0 ~ 12.0 2.9 ~ 3.3 1.1 ~ 1.3 ≤0.1 ≤0.1 ≤0.015 ≤0.015 余量 表 2 因素与水平
Table 2 Parameters and levels
水平 因素 激光功率 P/W 激光扫描速度 vs/(mm·s−1) 1 1 400 6 2 1 500 7 3 1 600 8 4 1 700 9 5 1 800 10 6 1 900 表 3 不同工艺参数成形的热输入
Table 3 Effect of linear energy density by different process parameters
扫描速度vs/(mm·s−1) 激光功率P/W 1 400 1 500 1 600 1 700 1 800 1 900 10 140 150 160 170 180 190 9 155 167 178 189 200 211 8 175 187 200 212 225 237 7 200 214 229 243 257 271 6 233 250 267 283 300 317 表 4 不同工艺参数成形AerMet100钢熔宽比
Table 4 AerMet100 steel melting width ratio formed by different process parameters
扫描速度vs/(mm·s−1) 激光功率P/W 1 400 1 500 1 600 1 700 1 800 1 900 10 0.92 0.95 0.99 1.06 1.10 1.13 9 0.96 0.98 1.04 1.10 1.13 1.17 8 0.99 1.03 1.08 1.13 1.20 1.25 7 1.01 1.08 1.12 1.22 1.21 1.31 6 1.07 1.13 1.19 1.23 1.26 1.39 表 5 优化后的工艺参数
Table 5 The optimized process parameters
编号 激光功率
P/W扫描速度
vs/(mm·s−1)激光热输入
E/(J·mm−1)1 1400 6 233 2 1500 7 214 3 1600 8 200 4 1700 10 170 5 1800 10 180 6 1900 10 190 表 6 试样的拉伸性能与冲击性能(25 ℃)
Table 6 Tensile properties and impact properties of LDM AerMet100 steel at 25 ℃
试样编号 屈服强度
Rel/MPa抗拉强度
Rm/MPa断后伸长率
A(%)冲击吸收能量
Akv2/J1 1465.8 1745.0 17.96 58 2 1396.4 1680.3 17.00 44.7 3 1391.3 1664.3 12.24 26.7 4 1585.50 1865.32 12.44 36.8 5 1612.42 1931.96 10.12 24 6 1560.21 1868.52 9.22 24 -
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