Fig. 1 shows a SEM micrograph of the cross-section of a plasma-sprayed Fe–Si–B–Cr–Mo metallic glass coating sprayed at plasma current of 300 A. In this case, the spraying distance was L= 50 mm. The primary plasma gas (Ar) flowratewas120 L/min, andthepowderfeedratewas32g/min(feedgasflowrate8 L/min) during the spraying time of 30s. A thick coating of 180?m and dense with low porosity was obtained at large plasma power of 300 A. It was revealed that the Fe-based metallic glass coating was compact, smooth, dense, free from pores, adhering well, and with no cracking. The porosity in the cross-section of the coating was a lower value of 2.4% at 300 A. The less pores of metallic glass coating indicated that the metallic glass particles did not undergo decomposition during plasma spraying. The value of the porosity of the coating depended on the plasma current. At a lower current of 200 A the value of porosity was 2.9%.
Fig. 1. SEM micrographs of the cross-section of the metallic glass sprayed at: plasma current of 300 A. Carrier gas of Ar flowrate:8 L/min,Arplasmagasflow rate: 120 L/min, spray distance: 50mm, and spray time: 30s.
Fig. 2. SEM micrographs of the surface of the metallic glass sprayed coating at plasma current of 300 A. This is the same coating as shown in Fig. 1
The surface morphology of the metallic glass coating was examined by the SEM. Fig. 2 shows the result of the same coating as in Fig. 1. The shape of individual deposit powder shows the melting condition of those powders was good. This means less porosity of the coating as was shown in Fig. 1. Many powders uniformly deposited on the surface of the stainless-steel substrate and formed metallic glass coating shown in Fig. 2.
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