Microstructural evolution and dissolution mechanisms of hard WC particles reinforced nickel based composite coatings fabricated by plasma transferred arc welding
Chunlin Zhang, Li Zhang, Yonghong Wang, Shengli Li, Jing Li, Zhiwen Xie
Abstract
Nickel based composite coatings reinforced with WC particles were fabricated using plasma transferred arc welding(PTAW) technique considering variable welding current and preheating operation. A detailed characterization was conducted to investigate the dissolution mechanism of WC particles and the microstructural evolution of the composite coatings . Results indicated that an increase in the welding current and preheating temperature result in a corresponding rise in dilution rate . Alloying reaction occurred between WC particles and the liquid nickel matrix within the molten pool, WC particles experienced decomposition-dissolution process, contributing to the formation of WC x and M x C y precipitated carbide phases. The trigonal and hollow hexagonal prisms are the basic three-dimensional morphology of in-situ synthesised WC and M 7 C 3 , respectively. Hard WC particles and precipitated carbide phases promote the hardness of the composite cladding coatings significantly together. The average hardness of the hard coating is between 669 and 756 HV, which is at least 2.4 times that of the substrate.