Inconel 600合金气体渗硼制备硬质陶瓷层的纳米力学性能和断裂韧性

来源期刊:中国有色金属学报(英文版)2020年第2期

论文作者:N. MAKUCH

文章页码:428 - 448

关键词:气体渗硼;硼化层;硬度;弹性模量;断裂韧性

Key words:gas boriding; borided layer; hardness; elastic modulus; fracture toughness

摘    要:采用气体渗硼法在Inconel600合金表面于N2-H2-BCl3气氛中制备陶瓷涂层。在920 °C和2 h 条件下所得涂层的显微组织中含有硼化铬和硼化镍混合物。研究硼化层的化学成分和相组成对其力学性能的影响。采用Berkovich 金刚石针在载荷为50 mN的条件下进行纳米压痕测试。结果表明,渗硼层具有较高的纳米压痕硬度 (HIT: 1542.6 HV~2228.7 HV)和弹性模量(EIT: 226.9~296.4 GPa)。HIT和EIT值增大是由于渗硼混合物层中硼化铬的比例较高。采用维氏微压痕技术测定在0.98 N载荷下的断裂韧性KC。结果显示,表面法向高压应力的存在导致渗硼层在断裂韧性方面具有很强的各向异性,所得最低断裂韧性值(0.5763 MPa·m1/2)和最高断裂韧性值(4.5794 MPa·m1/2)之间存在较大差异。造成这种情况的原因是测试区域的化学成分、相组成、孔隙度和残余应力存在差异。一般来说,铬含量较低的区域断裂韧性KC值较大。

Abstract: Gas-boriding in N2-H2-BCl3 atmosphere resulted in the formation of a thick layer on Inconel 600 alloy. The microstructure of layer produced at 920 °C for 2 h consisted of a mixture of chromium borides and nickel borides. The objective of investigations was to determine the influence of the chemical and phase compositions of borided layer on its mechanical properties. The nanoindentation was carried out using Berkovich diamond tip under a load of 50 mN. The gas-borided layer was characterized by high indentation hardness HIT from 1542.6 HV to 2228.7 HV and high elastic modulus EIT from 226.9 to 296.4 GPa. It was found that the mixture with higher percentage of chromium borides was the reason for the increase in HIT and EIT values. The fracture toughness (KC) was measured using Vickers microindentation technique under a load of 0.98 N. The presence of high compressive stresses in normal direction to the top surface caused the strong anisotropy of the borided layer, in respect of fracture toughness. The high difference between the lowest (0.5763 MPa·m1/2) and the highest (4.5794 MPa·m1/2) fracture toughness was obtained. This situation was caused by the differences in chemical and phase compositions of tested areas, presence of porosity and residual stresses. Generally, the higher KC values were obtained in areas with lower chromium content.

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