火焰喷涂NiCrBSi涂层的纳米力学性能

为揭示热喷涂涂层在不同尺度下的力学性能,在45钢基体上制备了平均厚度为750μm的火焰喷涂NiCrBSi涂层,利用纳米压痕技术研究了不同压痕深度下涂层表/截面力学性能、弹塑性和压痕变形行为。结果表明:涂层表/截面力学性能均呈现明显的尺寸效应,硬度、弹性模量、弹塑性随压入深度增加不断降低。涂层表面表现出高弹性,其压痕弹性功与总压痕功的比值ηIT在500nm深度内达到52%,而涂层截面为40%;涂层截面具有高硬度和高模量,其纳米硬度和弹性模量在2000nm深度内比涂层表面分别高28%和33%。涂层压痕变形表现为理想塑性、凹陷、凸起和裂纹等多种特征,随着压入深度增加,涂层表/截面弹塑性差异逐渐降低,并在2500nm深度同时下降到35%。涂层单一薄层结构在不同方向具有相同的硬度和弹性模量,但随压入深度增大,压头包含的涂层体积增大,相邻薄层,特别是孔隙、裂纹、层间边界等缺陷对涂层性能的影响逐渐增强,导致涂层表/截面硬度和弹性模量的差异性随压痕深度增加不断降低。

Nano Mechanical Properties of Flame Sprayed NiCrBSi Coating

To reveal the mechanical properties of thermal spray coating on different scales ,flame spray NiCrBSi coating with average thickness 750μm was prepared on 45 carbon steel substrate ,the me-chanical properties ,elastic-plasticity and indentation deformation of coating surface and cross-section were studied by nanoindentation .Results indicate that scale-dependent behaviors of coating mechani-cal properties were observed as a function of indentation depth for either the coating surface or the cross-section .The nano hardness ,modulus and elastic-plasticity of coating decrease with the increas-ing indentation depth .The coating surface exhibits higher elasticity than the coating cross-section ,the ratio of elastic work to the total indentation work ,ηIT ,of coating surface is 52％ at the depth of 500nm ,while that of coating cross-section is 40％ ;moreover , the coating cross-section possesses higher hardness and modulus than the coating surface ;the corresponding values of the coating cross-section are 28％ and 33％ at the depth of 2000nm ,higher than those of the coating surface ,respec-tively .The indentation marks show ideal plastic deformation ,pile-up and sink-in ,and cracks .The difference of ηIT values between coating surface and cross-section decreases with the increasing indenta-tion depth .It reaches about 35％ at the depth of 2500nm from the both coating directions .For the coating splat structure ,hardness and elastic modulus are the same in different directions ,besides ,with the increasing indentation depth ,larger volume is involved in the indentation . The influence of the surrounding splats (especially the pores ,cracks or grain/splat boundaries ) on the measured coating properties is enhanced gradually ,leading to differences in the appearance between different coating di-rections ,as well as the decrease of coating hardness ,elastic modulus.