Prediction of Blistering in Coating Systems

Engineering Failure Analysis

2017

This paper contains a review of the most vital concepts regarding the analysis and design of film systems. Various techniques have been presented to analyse and predict the failure of films for all common types of failure: fracture, delamination, general yield, cathodic blistering, erosive and corrosive wear in both organic and inorganic films. Interfacial fracture or delamination is the loss of bonding strength of film from substrate, and is normally analysed based on the fracture mechanics concepts of bi-material systems. Therefore, keeping the focus of this review on bonding strength, the emphasis will be on the interfacial cracking of films and the corresponding stresses responsible for driving the delamination process. The bi-material characteristics of film systems make the nature of interfacial cracks as mixed mode, with cracks exhibiting various complex patterns such as telephone cord blisters. Such interfacial fracture phenomenon has been widely studied by using fracture mechanics based applicable analysis to model and predict the fracture strength of interface in film systems. The incorporation of interfacial fracture mechanics concepts with the thermodynamics/diffusion concepts further leads to the development of corrosive degradation theories of film systems such as cathodic blistering. This review presents the suggestions for improvements in existing analysis techniques to overcome some of the limitations in film failure modelling. This comprehensive review will help researchers, scientists, and academics to understand, develop and improve the existing models and methods of film-substrate systems.

Section: Cathodic Blisteringmentioning

confidence: 99%

Section: Other Models For Cathodic Blisteringmentioning

confidence: 99%

Section: Future Scientific Challenges In Degradation Modellingmentioning

confidence: 99%

See 1 more Smart Citation

A review of theoretical analysis techniques for cracking and corrosive degradation of film-substrate systems

Engineering Failure Analysis

2017

“…However, in some circumstances this attack is promoted, rather than hindered, and this results in the delamination of coatings [1]. There are several causes of coating delamination such as micro-defects at the coating substrate interface and micro-cracks in coatings [2,3].…”

Section: Introductionmentioning

confidence: 99%

Analysing the coupled effects of compressive and diffusion induced stresses on the nucleation and propagation of circular coating blisters in the presence of micro-cracks

Engineering Failure Analysis

Stokes

2016

This paper presents the delamination of coating with micro-cracks under compressive residual stress coupled with diffusion induced stress. Micro-cracks in coating provide a passage for corrosive species towards the coating-substrate interface which in turn produces diffusion induced stress in the coating. Micro-cracks contract gradually with increasing compressive residual stress in coating due to thermal expansion mismatch which blocks the species diffusion towards the interface. This behaviour reduces the diffusion induced stress in the coating while the compressive residual stress increases. With further increase in compressive residual stress, micro-cracks reach to the point, where they cannot be constricted any further and a high compressive residual stress causes the coating to buckle away from the substrate resulting in delamination and therefore initiating blistering. Blistering causes the contracted micro-cracks to wide open again which increases diffusion induced stress along with high compressive residual stress. The high resultant stress in coating causes the blister to propagate in an axis-symmetric circular pattern. A two-part theoretical approach has been utilised coupling the thermodynamic concepts with the mechanics concepts. The thermodynamic concepts involve the corrosive species transportation through micro-cracks under increasing compression, eventually causing blistering, while the fracture mechanics concepts are used to treat the blister growth as circular defect propagation. The influences of moduli ratio, thickness ratio, thermal mismatch ratio, poisson's ratio and interface roughness on blister growth are discussed. Experiment is reported for blistering to allow visualisation of interface and to permit coupled (diffusion and residual) stresses in the coating over a full range of interest. The predictions from model show excellent, quantitative agreement with the experimental results.

“…However, in some circumstances, this attack is promoted, rather than hindered, and results in blister initiation. [28] There are several causes of blister initiation: artificial defects and pores in coatings [29,30] and micro-cracks [31] leading to the substrate. These defects provide channels for water and oxygen to diffuse towards the metal/coating interface.…”

Section: Introductionmentioning

confidence: 99%

A unified mathematical modelling and simulation for cathodic blistering mechanism incorporating diffusion and fracture mechanics concepts

Journal of Adhesion Science and Technology

Stokes

2015

A novel mathematical model has been developed to understand the mechanism of blister initiation and propagation. The model employs a two-part theoretical approach encompassing the debondment of a coating film from the substrate, coupled with the design components incorporating diffusion and fracture mechanics, where the latter is derived from equi-biaxial tensile loading. Integrating the two components, a comprehensive mathematical design for the propagation of blister boundaries based on specific toughness functions and mode adjustment parameters has been developed. This approach provided a reliable and efficient prediction method for blister growth rate and mechanisms. The model provided a foundation for holistic design based on diffusion and mechanic components to enable better understanding of the debondment of thin elastic films bonded to a metallic substrate.