Microstructure and wear resistance of molybdenum based amorphous nanocrystalline alloy coating fabricated by atmospheric plasma spraying

Molybdenum (Mo) based amorphous nanocrystalline coating was deposited on the surface of plain carbon steel substrates by atmospheric plasma spraying (APS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the microstructures of Mo-based powder and coating. The surface hardness of substrate and coating were determined using a Vickers hardness tester, and microhardness profile of cross-section was realized by a Vickers microhardness tester. Wear tests were carried out using a pin on plate type tester by changing the load and linear speed. The results indicated that the as-prepared Mo-based coating was mainly composed of Fe0.54Mo0.73, Fe3Mo, Cr9Mo21Ni20, Fe3B and Cr0.46M0.4Si0.14 phases. The average grain size of Mo-based coating was 22-32 nm. The coating presented a dense layered structure and its thickness was about 250 mu m. The surface hardness of Mo-based coating was as high as 9.2 GPa, which was 8 times of substrate. The microhardness along the cross-section gradually decreased from coating to substrate. The wear resistance of Mo-based coating was far better than that of substrate. (C) 2012 Elsevier B.V. All rights reserved.