| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 99 === In this research, Co-based alloy Stellite6（Co-28Cr-4W-1.1C）and Ni-based alloy Deloro60（Ni-14.4Cr-3.2B-4.4Si）were clad on carbon steel using high frequency induction heating. With different processing parameters, the properties of the clad layer were studied through observing the microstructure, measuring the chemical composition and hardness distribution, indentifying the phases in the layer, and conducting the corrosion test.
The results show that the microstructure of Co-based alloy layer can be divided into dendrite, interdendritic eutectics and needle structure. If the microstructure of the clad layer is dendrite and interdendritic eutectics, the matrix is Co-rich solid solution containing chromium, iron and other elements with network M7C3 carbide distributed along the grain boundary. The hardness of the clad layer will decrease with increasing the heating time. However, when the content of iron is more than 40％, the microstructure will transform into needle structure, and the hardness of the clad layer will increase with increasing the heating time.
Ni-based alloy layer consists of γ-Ni matrix, Ni3B, Ni31Si12, CrB, Cr7C3 and Ni-Cr-Fe compounds. The interface compound of Ni-Cr-Fe will increase and both CrB and Cr7C3 will decrease with increasing the heating time, leading to a slightly decrease in the hardness near the interface. In the clad layer, the coarsening of CrB and Cr7C3 becomes more obvious as the heating time increases. In other words, the volume fraction of hardening phases（CrB and Cr7C3）increases and lead to the increasing of hardness. High heating power and short heating time will increase the compounds of CrB and Cr7C3 as well as the volume fraction ofγ-Ni and Ni3B ,and lead to increase in hardness of the clad layer.
The specimen clad with Co-based alloy or Ni-based alloy has excellent resistance to the corrosion of hydrochloric acid, nitric acid and sulfuric acid. No matter which alloy is clad, the ability of anti-corrosion will decrease with increasing the heating time, owing to the dilution of iron in the clad layer.
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