Fracture Behavior of a Brittle Coating on a
Strained Ductile Substrate

YANG Banquan^{1, 2, 3}  CHEN Guangnan¹  ZHANG Kun¹  LUO Gengxing¹  XIAO Jinghua¹

(1. Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190;
2. Department of Mechanical Engineering, The Academy of Armored Forces of PLA, Beijing 100072;
3. Graduate School, Chinese Academy of Sciences, Beijing 100190)

Abstract: An elastic-plastic interface layer between a brittle coating and a ductile substrate is presented to investigate the fracture behavior of the brittle coating on the ductile substrate under the tensile load. Using a modified shear-lag model, the analytical solutions for the distribution laws of the tensile stress developed in the coating, the shear stress developed along the interface and the relationship between the crack density of the brittle coating and the applied strain of the substrate can be obtained. These analytical results are applied to investigate the fracture behavior of a hard and brittle chromium coating on a normal medium carbon steel substrate. The experiment results show that the average saturated crack density of the brittle chromium coating has a good agreement with that predicted by the solution presented .

Key words: Brittle coating  Ductile substrate  Elastic-plastic interface layer  Tensile strain  Fracture characterization

CLC No: TB302.3 TG115.5

国家自然科学基金重点资助项目(50531060). Received 20070524, received in revised form 20071220

References

[1] FREUND L B, SURESH S. Thin film materials, stress, defect formation and surface evolution[M]. Cambridge: Cambridge University Press, 2003.
[2] XU Biushi, ZHU Shaohua. The theory and technology of surface engineering [M]. Beijing: Defense Iudustry Press, 1999.
[3] GILES A S, NIGEL J, JONATHAN H. Adhesion of thin coatings—the VAMAS (TWA 22-2) interlaboratory exercise[J]. Surface and Coatings Technology, 2005, 197(2-3): 336-344.
[4] XIE C J, WEI T. Cracking and decohesion of a thin Al2O3 film on a ductile Al-5%Mg substrate[J]. Acta. Materialia, 2005, 53(2): 477-485.
[5] AGRAWAL D C, RAJ R. Measurement of the ultimate shear strength of a Metal-Ceramic interface[J]. Acta. Metallurgica, 1989, 37 (4): 1 265-1 270.
[6] CHEN B F, HWANG J, CHEN I F, et al. A tensile film cracking model for evaluating interfacial shear strength of elastic film on ductile substrate[J]. Surface and Coatings Technology, 2000, 126(2-3): 91-95.
[7] SHIEU F S, SHIAO M H. Measurement of the interfacial mechanical properties of a thin ceramic coating on ductile substrates[J]. Thin Solid Films, 1997, 306(1): 124-129.
[8] COX H L. The elasticity and strength of paper and other fibrous materials[J]. British Journal of Applied physics, 1952, 3: 72-79.
[9] SOPOK S, RICKARD C, DUNN S. Thermal-chemical- mechanical gun bore erosion of an advanced artillery system part one: theories and mechanisms [J]. Wear, 2005, 258(1-4): 659-670.
[10] UNDERWOOD J H, WITHERELL M D, SOPOK S, et al. Thermomechanical modeling of transient thermal dama- ge in cannon bore materials[J]. Wear, 2004, 257(9-10): 992-998.
[11] ZHUO Huiru. Collections of the life prediction for gun tube[M]. Beijing: Institute of 208, Weapon Industry of China, 1996.
[12] MA X Q, CHO S, TAKEMOTO M. Acoustic emission source analysis of plasma sprayed thermal barrier coatings during four-point bend tests[J]. Surface and Coatings Technology, 2001, 139(1): 55-62.