Page 15 - 摩擦学学报2025年第4期

第 4 期 束坤, 等: 接触几何参数对硬质薄膜断裂和分层失效行为的影响及其解耦分析 503

3. Zhengzhou Research Institute, Harbin Institute of Technology, Henan Zhengzhou 450046, China)
Abstract: Film fracture (cohesive failure) and interfacial delamination (adhesive failure) are two main damage modes of
thin hard solid films on elastic-plastic steel substrates, and their initiation and propagation processes have complex
coupling relationships. Tensile stress concentrations induced by the bending and stretching effects at film surfaces, and
concentrations of tensile and shear stresses caused by the mismatch of elastoplastic deformation at the film/substrate
interfaces, are the critical reasons for film fracture and interfacial delamination, respectively. Distribution and evolution
behaviors of the film principal stress and the interfacial stress during spherical micro-indentations of thin hard films on
elastic-plastic steel substrates were analyzed using the finite element method in this article. Influences of the contact
geometric parameter t/R (the ratio of film thickness and spherical indenter radius) on the film fracture and the interfacial
delamination were investigated, and the guideline of the decoupling analysis for those two failure behaviors were
explored, which provided theoretical guidance for the characterizations of the cohesive and adhesive properties of film-
substrate systems. Results indicated that the loading process of a micro-indentation test on a film-substrate system could
be roughly divided into three main stages according to the position of the maximum plastic deformation of the substrate:
film bearing stage (Stage I), film-substrate common bearing stage (Stage II), and substrate bearing stage (Stage III). The
deformation states of the film were elastic smooth deformation, bending deformation, and tensile deformation,
respectively. For the system with a large t/R (t/R ≥ 0.08), the main bearing stage were Stage I and Stage II, and the
maximum tensile principal stress of the film was always located in the bottom bending deformation zone; For the system
with a small t/R (t/R ≤ 0.01), the main bearing stage was Stage III, and the maximum tensile principal stress of the film
was always located in the surface stretching deformation zone at the outer edge of the contact area; For the system with
0.02 ≤ t/R ≤ 0.067, the main bearing stage transferred from Stage II to Stage III as the indentation depth increase, and
the maximum tensile principal stress of the film shifted from the bottom bending zone to the surface stretching zone at
the outer edge of the contact area. The potential fracture form changed from radial cracks to ring cracks, and there was a
linear corresponding relationship between the critical indentation depth as well as the critical stress of the position
transferring point of the main stress (i.e. film potential fracture form) and the parameter of t/R. With the increase of t/R,
the maximum normal stress at the interface both increased during the loading and unloading processes, and the
possibility of I-type tensile delamination increased, while the maximum tangential stress at the interface slightly
decreased. However, due to the substrate plastic deformation, maximum tangential stresses at interfaces were close to its
√
shear yield strength of 0.6σ ys ( 1/ 3σ ys , σ ys is the substrate yield strength). To avoid the coupling influences of fracture
and delamination, a larger t/R should be applied to evaluate the normal adhesive performance at interfaces; While to
analyze the tangential adhesive properties a smaller t/R was the preference due to the relatively small impact of t/R on
tangential stresses at interfaces and the high risk of film cracking caused by a larger t/R.
Key words: thin hard solid film; contact geometric parameter; decoupling analysis; film fracture; interfacial
delamination; finite element analysis

随着表面工程技术的快速发展，具有优异抗磨减 的显著影响 [12-16] . 与此同时，不同损伤失效形式之间的
摩性能、良好经济适用性和环境友好性的硬质固体薄 相互影响进一步加剧了其渐进性演化过程的复杂性.
膜被广泛应用于齿轮、轴承和活塞等零部件的摩擦表 例如，Abdul等 和肖洋轶等 研究发现压痕作用下
[17]
[18]
界面的润滑和防护 [1-5] . 然而，薄膜自身的聚合(cohesive) 硬质薄膜抗断裂能力的提高会增加界面分层的风险；
[19]
性能和薄膜/基体的结合(adhesive)性能不足导致的薄 而钟向丽等 则发现界面分层会加剧薄膜裂纹的扩
膜断裂和界面分层 [6-8] ，严重阻碍了其在高速、高精度 展. 笔者前期研究结果也表明：接触区内，界面分层促
和高可靠装备领域的工程应用. 进薄膜底部断裂；而接触区外，界面分层降低薄膜表
[20]
薄膜表面弯曲、拉伸导致的拉应力集中和膜基界 面裂纹 . 因此，面向高接触应力下硬质薄膜断裂分
面处弹塑性变形失配导致的拉伸和剪切应力集中，分 层竞争耦合失效，开展基于损伤失效控制机理的加载
别是引起薄膜断裂和界面分层的主要原因 [9-13] ，并且 测试条件调控，实现多源损伤失效行为的解耦表征分

其损伤失效过程受到系统本征材料参数(弹性模量、 析，对于薄膜材料性能的定量测评具有重要意义.
屈服强度、断裂强度和韧性等)、接触几何参数(薄膜 压痕特别是球形纳/微米压痕测试是目前最为常
厚度、接触配副尺寸等)及接触界面参数(摩擦系数等) 用的膜基系统材料级试验评价分析方法之一. 压头尺