激光熔覆CoCrFeMnNiMox高熵合金涂层的微观组织及性能

doi:10.16183/j.cnki.jsjtu.2021.201

摘要/Abstract

摘要：

45钢存在耐磨性能及耐蚀性能较差等问题.采用激光熔覆技术在45钢表面制备了CoCrFeMnNiMo_x(x=0.00, 0.25, 0.50, 0.75, 1.00)高熵合金涂层,研究了Mo元素对高熵合金涂层的微观组织和性能的影响.结果表明:CoCrFeMnNiMo_x高熵合金涂层由单一的面心立方(FCC)固溶体组成.含Mo元素涂层微观结构为典型的枝晶和枝晶间结构,这是熔池在凝固过程中的非均质形核现象导致的.涂层的显微硬度随x值的增大而升高,其中Mo_1.00涂层硬度最高为2.391 GPa,定量计算表明固溶强化是显微硬度提升的主要原因.随着Mo质量分数的升高,磨损机制从黏着磨损演变为磨粒磨损和氧化磨损.其中,Mo_1.00涂层具有最低的体积磨损率(0.68×10^-4 mm³/(N·m)).根据点缺陷模型理论分析了涂层钝化对耐蚀性能的影响.添加Mo元素提升了涂层钝化行为的脱水速率,使得氧化物层变厚,进而提升了涂层的耐蚀性.涂层的腐蚀机制为晶间腐蚀,Mo_0.75涂层具有最小的自腐蚀电流密度和最正的自腐蚀电位,分别为3.69×10^-6 A/cm²和 -0.432 V.

关键词: 激光熔覆, 高熵合金, 显微硬度, 磨损机制, 腐蚀机制

Abstract:

45 steel has the problems of low wear resistance and poor corrosion resistance. CoCrFeMnNiMo_x (x=0.00, 0.25, 0.50, 0.75, 1.00) high-entropy alloy coating was prepared on 45 steel by laser cladding. The influence of Mo on the microstructure and properties of coating were explored in detail. The results show that the CoCrFeMnNiMo_x high-entropy alloy coating is composed of a single face-centered cubic (FCC)solid-solution phase. The microstructure of the Mo-containing coating is a typical dendritic and interdendritic structure, which is caused by the heterogeneous nucleation of the molten pool during the solidification process. The microhardness of the coating increases with the increase of x, and the maximum microhardness of the Mo_1.00 coating is 2.391 GPa. Quantitative calculations show that solution strengthening is the main reason for the increase of microhardness. With the increase of Mo mass fraction, the wear mechanism evolves from adhesive wear to abrasive wear and oxidative wear. The Mo_1.00 coating has the lowest volume wear rate (0.68×10^-4 mm³/(N·m)). The influence of the passivation process on the corrosion resistance of coating was analyzed based on the point defect model theory. The addition of the Mo element increases the dehydration rate of the passivation behavior of coating, which makes the oxide layer thicker, and thereby improving the corrosion resistance of coating. The corrosion mechanism of coatings is intergranular corrosion. Mo_0.75 coating has the smallest self-corrosion current density and the most positive self-corrosion potential, which are 3.69×10^-6 A/cm² and -0.432 V, respectively.

Key words: laser cladding, high-entropy alloys, microhardness, wear mechanism, corrosion mechanism

中图分类号:

TN249
TG174

刘昊, 孙世峰, 李晓佳, 郝敬宾, 杨海峰. 激光熔覆CoCrFeMnNiMo_x高熵合金涂层的微观组织及性能[J]. 上海交通大学学报, 2022, 56(12): 1675-1687.

LIU Hao, SUN Shifeng, LI Xiaojia, HAO Jingbin, YANG Haifeng. Microstructure and Properties of CoCrFeMnNiMo_x High-Entropy Alloy Coating by Laser Cladding[J]. Journal of Shanghai Jiao Tong University, 2022, 56(12): 1675-1687.

图/表 19

表1

图1

图2

图3

图4

图5

表2

图6

图7

表3

图8

图9

表4

CoCrFeMnNiMox高熵合金涂层的平均温度与闪点温度计算结果

涂层	A_n/mm²	$F -$	$V -$	N	T_b/K	T_f/K
Mo_0.00	1.83×10^-2	0.16	70.12	1854	360.43	384.41
Mo_0.25	0.63×10^-2	0.47	45.83	1461	410.75	445.41
Mo_0.50	1.58×10^-2	0.19	67.31	1918	350.99	369.77
Mo_0.75	1.24×10^-2	0.24	53.85	1467	362.19	387.66
Mo_1.00	0.50×10^-2	0.59	37.15	935	419.23	464.66

表4

图10

图11

图12

表5

图13

图14

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元素	1	2	3	4	5	6	7	8
Cr	7.71	8.67	6.82	10.59	6.56	7.88	5.91	6.29
Mn	7.36	9.97	7.12	8.39	6.37	7.69	5.07	6.85
Fe	60.94	53.13	63.17	43.85	60.37	52.98	62.44	59.71
Co	9.98	9.24	9.00	6.48	9.85	8.60	7.95	7.29
Ni	10.23	10.04	9.35	6.13	9.31	10.13	12.25	5.71
Mo	3.20	8.94	4.54	24.56	7.54	12.71	6.38	14.15

涂层	H₀	H_SS	H_C	H_exp
Mo_0.25	1.77	0.201	1.971	1.947±0.07
Mo_0.50	1.77	0.397	2.167	2.128±0.09
Mo_0.75	1.77	0.492	2.262	2.266±0.02
Mo_1.00	1.77	0.596	2.365	2.396±0.04

涂层	E_p/V	E_tr/V	E_w/V	I_mp/(A·cm^-2)	I_coor/(A·cm^-2)	E_coor/V
Mo_0.00	-0.427	0.058	0.485	3.97×10^-4	7.36×10^-6	-0.466
Mo_0.25	-0.450	0.529	0.979	1.52×10^-4	3.93×10^-6	-0.487
Mo_0.50	-0.441	0.417	0.858	1.32×10^-4	5.26×10^-6	-0.471
Mo_0.75	-0.402	0.337	0.739	2.56×10^-5	3.69×10^-6	-0.432
Mo_1.00	-0.447	0.481	0.928	1.24×10^-4	5.95×10^-6	-0.479