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Vol.56, No.4, 280 ~ 289, 2018
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| Title |
| Effects of Heat Treatment and Thermal Cycle Conditions on the Bonding Strength and Interfacial Characteristics of Electroplated Cr/Electroplated Ni-P Coatings |
| 이진아 Jina Lee , 손기락 Kirak Son , 최명희 Myung-hee Choi , 이규환 Kyu Hwan Lee , 박영배 Young-bae Park |
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| Abstract |
| The effects of heat treatment and thermal cycle conditions on the bonding strength and interfacial characteristics of electroplated Cr/electroplated Ni-P coatings were systematically evaluated. With step1 samples, heat treatment was performed at 750 ℃ for 6 hours after successive electroplating of Ni-P and Cr layers. With step2 samples, 1st heat treatment was performed at 500 ℃ for 3 hours after electroplating Ni- P, and then 2nd heat treatment was performed at 750 ℃ for 6 hours after electroplating Cr. The bonding strengths measured by ASTM C633 were around 54.6 MPa before thermal cycling, and decreased to 35 MPa and 29.9 MPa for the step1 and the step2, respectively, after 1,000 cycles between 150~600 ℃. Increasing the number of thermal cycles led to an increasing adhesive/Cr interface delaminated mode, which seemed to be closely related to the decreaed bonding strength possibly due to severe surface Cr oxidation. Also, the higher residual stress was investigated in the step1 than step2 samples. It is thought to be responsible for the higher density of channeling cracks in the Cr layer, which led to slightly stronger bonding strength due to the mechanical interlocking effects of the adhesive inside the channeling cracks. |
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| Key Words |
| metals, plating, microstructure, tensile test, thermal cycle |
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