Browsing by Author "Sheu, Hung-Hua"

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Effect of Pretreatment Process on the Adhesion and Corrosion Resistance of Nickel-Boron Coatings Deposited on 8620H Alloy Steel
(2020-01-01)
Cheng, An-Yu
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Sheu, Hung-Hua
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Liu, Yih-Ming
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Hou, Kung-Hsu
;
Hsieh, Pei-Yi
In this work, Ni-B coatings were electrodeposited on the 8620H steel substrates, the substrates were carried out with different pretreatment including without pretreatment, after sandblasting by glass sand and after sandblasting by emery powders. The results of scratch test indicated that the best adhesion strength of Ni-B coatings occurred at the 8620H steel substrates carried out with sandblasting by emery powders, the Ni-B coatings still did not be damaged when the load increase to 50 N. The values of Ni-B coatings deposited on different pretreatment condition such as without pretreatment, after sandblasting by glass sand and after sandblasting by emery powders are approximately at 9.46x 10(-6), 8.62x 10(-6) and 2.31 x 10(-6) A/dm(2), respectively. All the samples carried out with a wear process at a load of 20 N, the icorr values of Ni-B coatings deposited on different conditions 1.96x 10(-5), 1.54x 10(-5) and 6.72x 10(-6) A/dm(2), respectively. The results show that the Ni-B coatings deposited on the 8620H steel substrates carried out with sandblasting by emery powders has the best adhesion strength and corrosion resistance due to the Ni-B coatings did not be damaged during wear process.
Effect of Saccharose Concentration and Temperature on the Internal Stress and Corrosion Resistance of Electroplated Chromium Coatings Prepared from Chromium (III) Bath
(2020-04-01)
Sheu, Hung-Hua
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Chen, Yuan-Rong
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Ger, Ming-Der
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交大名義發表
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National Chiao Tung University
The trivalent chromium carbon coatings are electroplated from different electroplating temperature (10, 0 and -5 degrees C) and different concentration (0.01, 0.02 and 0.03 M) of saccharose (C12H22O11). The saccharose play a role of stress inhibitor in the bath during electroplating process. The results of internal stress analysis show that the internal stress of the trivalent chromium carbon coating decreases with the increase of concentration of saccharose at individual electroplating temperatures, this shows that saccharose has the effect on suppressing the accumulation of stress within the coating. Moreover, the electroplating temperature also affect the internal stress of trivalent chromium carbon coatings i.e. the lower electroplating temperature (-5 degrees C) will reduce the accumulation of stress within the coating during electroplating. The smallest internal stress of trivalent chromium carbon coatings is 13.4 MPa, electroplated at -5 degrees C with a concentration of saccharose at 0.02 M. The best i(corr) is approximately at 1.32x 10(-6) A/dm(2), this coatings is also electroplated at -5 degrees C and the concentration of saccharose at 0.02 M. The results indicated that both electroplating temperature and concentration of saccharose can reduce the internal stress within trivalent chromium carbon coatings and decrease the through-deposit cracking within coatings, thereby improving the corrosion resistance of coatings.
The effects of graphene content on the mechanical properties and thermal conductivity of Inconel 718 superalloy brazed using BNi-2/graphene composite filler metal
(2020-03-01)
Lee, I-Kon
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Sheu, Hung-Hua
;
Hsu, Heng-Yao
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交大名義發表
;
National Chiao Tung University
The graphene/BNi-2 filler composites (G-BNi-2) with different graphene contents were used to braze Inconel 718 superalloy in a vacuum furnace. The wettability between different graphene contents of composite G-BNi-2 filler and Inconel 718 superalloy were analyzed after brazing, and all the contact angles of composite filler with different graphene contents on Inconel 718 were lower than 70 degrees, indicating that all the BNi-2 filler and G-BNi-2 composite fillers have good affinity with the Inconel 718. The typical interfacial microstructure of the brazing samples and the formed intermetallic compounds are analyzed with EDS, SEM, XRD and TEM. The effects of the graphene content on the microstructure of brazing area and mechanical properties such as microhardness and shear strength were investigated. The shear strength of brazed sample using BNi-2 filler was approximately 378.9 MPa. The highest shear strength of 390.8 MPa was achieved for brazed specimen using G-BNi-2 composite filler with 0.03 wt% graphene. However, above this graphene content, the shear strength progressively decreases as the graphene content increases. The highest thermal conductivity of 22.7 W/m center dot K was achieved for brazed sample using the composite filler with the highest graphene content (0.07 wt%).