The Integration Of Automatic Scratching Detecting System Of Laser And Experimental Research On Bonding Strength Of Interface Of Film-Substrate

Bonding strength of interface of the film-substrate is one of important criterions to estimate the film quality.It is also the key problem that influences the reliability and usage of film-substrate system.It aims to detect the bonding strength of interface more dependable;many domestic and foreign researchers have developed a great deal of research and have achieved many important research results.Laser scratching & detecting technique is a new type of non contact technique,which was created by laser technique combined with traditional scratching technique,to detect bonding strength of interface.The principle is that the coating is broken off from substrate,when the coating sample is radiated directly by laser with different power through a quasistatic method. At the same time,the coating which relatives to laser-beam is moved.The laser parameters,detect parameters of critical broken position and physical properties parameters of materials are used to represent bonding strength of the interface.Firstly,several normal methods of detecting bonding strength of interface and laser scratching technique are introduced in the paper.Then the experimental equipments,detecting principles and relevant automatic scratching & detecting system integration softwares are also introduced emphatically.According to theoretical analysis on the coating which is scratched by infrared laser,it is indicated that the peel off stressσ_剥（x） and cut stressτ_zx（x） have important effects on bonding strength of interface.It is also concluded that the temperature field（T） generated when the coat is scratched by laser has relevant to laser power（P）,absorptivity of material surface（β）,thermal conductivity of material（c_p）,beam diameter（d） and scratch speed（v） etc.Furthermore, it also explains in the paper that these parameters can reflect bonding strength of the interface between the coating and substrate.According to experimental research and detecting results analyzed by infrared image apparatus when the coating is scratched by laser,it is indicated that the change of surface temperature of coating presents a two-phase process,which corresponds with the results of theoretical analysis.The turning point of temperature is just the critical position where the coating breaks off from substrate. According to experimental research on non-bounding layer TiN film coating made by PVD process,which is shock-scratched by Nd:YAG pulsed-laser.The research results indicate the surface residual pressure stress of coating shock-scratched by laser with increasing power density was diminished significantly,and the gradual increscent residual tension stress was generated in the positions which are affected heavily by laser.In addition,the shock waves generated when coating is shock-scratched by laser have an obvious effect on interfacial bonding strength,the strong shock waves can led to the coating is obviously warped,crazed and broken when the laser energy density was large enough.