| The residual stress level of the coating is a key factor to influence the performance,reliability and durability of the coated part.However the control of intrinsic stress can effectively adjust the residual stress level of the coating.For energy deposition techniques,ion bombardment is a factor that affects residual stress independent of coating growth and can significantly influence the intrinsic stress.In this paper,two typical energy deposition techniques,modulated pulsed power magnetron sputtering(MPPMS)and deep oscillation magnetron sputtering(DOMS),are used to control ionization rate of the deposition flux.By establishing the discharge characteristics of the two techniques,the residual stress evolution regulation of hard Cr coatings deposited by the two techniques is analyzed,and the influence of time variation of deposition flux on residual stress is further studied.The main conclusions are listed as follows:(1)The MPPMS and DOMS discharge are more characteristic than HiPIMS.The MPPMS strong ionization stage and DOMS discharge are further analyzed based on the HiPIMS discharge regulation.The MPPMS strong ionization stage discharge is mainly divided into four stages: the first stage is the current rising stage,the second stage is the gas rarefaction stage,the third stage is the current platform value stage,and the fourth stage is the afterglow stage.The DOMS discharge process is mainly divided into three stages: the first stage is the current rising stage,the second stage is the gas rarefaction stage,and the third stage is the afterglow stage.Comparing the two techniques with average power,DOMS discharge peak current,peak voltage and peak power are significantly higher than MPPMS,indicating that the ionization rate of particles in DOMS deposition flux is higher.(2)Due to the different discharge characteristics of MPPMS and DOMS,the structure and mechanical properties of the deposited Cr coating are significantly different.The Cr coating deposited by both forms a fine-grained structure when the coating thickness is small,and gradually changes to a columnar crystal structure as the coating thickness increases.The structure of the Cr coating by deposited DOMS is denser.The residual stress of the Cr coating deposited by both is compressive stress when the initial coating is 0.1 ?m.However,the residual compressive stress of the Cr coating deposited by DOMS is much larger than that of MPPMS.As the coating thickness increases,the stresses of the same thickness coating are almost the same.When the coating thickness reaches 1.5 ?m,the residual stress of the Cr coating deposited by DOMS is still a small compressive stress,while the residual stress of the Cr coating deposited by MPPMS gradually changes to the tensile stress.(3)Based on the interaction between the adsorption atom migration during the growth of the coating interrupted deposition flux and the growth stress,and the influences of the interruption time and the number of interruptions on the coating residual stress and bonding force are investigated.When the deposition conditions are the same,the number of interruptions and the interruption time of the deposition flux are changed in the first 600 s of the DOMS deposition,and a 1.5 ?m coating is deposited that the residual stress is equivalent to that of the continuously deposited coating.However,the film-based bonding force of the Cr coating is influenced by the interruption time and the number of interruptions.According to the scratch morphology,it is found that the film-based bonding force of the Cr coating is significantly improved,for example three interruptions and the interruption time is 40 s.The comparison of Cr coating deposited by MPPMS and DOMS shows that the intrinsic stress can effectively control the coating residual stress,and the impact of ion bombardment on the residual stress is more significant in the initial stage of the coating growth. |
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