In this study, FeCrB coatings are deposited by wire arc spraying using powder cored wires to investigate the factors that affect thermal conductivity. Experimental results show that increasing boron content in the wires reduces oxide content in the coatings, which increases thermal conductivity. Annealing also increases thermal conductivity, which can be explained by grain growth and a reduction in porosity.

A series of FeCrBCSi coatings were prepared by two-roll wire-arc spraying to investigate the influence of the boron content on the microstructure and properties of the coatings. Microstructural studies show that the as-deposited coatings present a dense layered structure with the porosity around 3%, and are primarily composed of a composite structure of amorphous phase and nanocrystalline phase. It is found that the addition of boron content within the composition range examined exhibits a significant effect on the phase component, as well as the microhardness and wear resistance of the coatings. The optimal composite phase structure, in terms of higher amorphous fraction and lesser nanocrystalline size distribution, leads to the relatively best performance of the coating with 26% boron added. The relative wear resistance of this coating is about 18 and 4 times higher than that of the Q235 steel and commercially available SHS 7170 coating, respectively, therefore wire-arc sprayed FeCrBCSi coating could be an effective and economic approach to withstand wear environment.

In this paper, Ni-based cored wires were prepared by using NiCr strip to wrap metal powders of Ni, Cr, Mo, CrB. Ni-based coatings were prepared by electric arc spraying process. The microstructures of Ni-Cr-Mo and Ni-Cr-B coatings were investigated by means of scanning electron microscopy (SEM) and energy-dispersive analysis (EDAX) and X-ray diffraction (XRD) analysis. The coatings have compact surface and presented the bonding strength higher than 40MPa. Corrosion-resistance performance of coatings was evaluated by salt-spray- test and electrochemical corrosion test. The results showed that Ni-based coatings containing Mo (5%) element or B element (2-4%) had better anti-chlorine ion corrosion performance than that of Ni-based coatings without Mo element, and PS45 (Ni-Cr-Ti) coating. The anti-chlorine ion corrosion coatings could be used for resolving the corrosion protection problem of the equipments and piping contacting sour, alkali, salt liquid in the petrochemical engineering.

Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. As commercial arc sprayed coatings have been used to a limited extent in applications involving erosion and abrasion wear, developing attractive wear resistance arc sprayed coatings has been found necessary. Abrasive wear testing was carried out on four Fe-based composite coatings containing varied contents of Cr 3 C 2 particles as hard phases. Scanning electron microscopy (SEM) was used for observing the surfaces of the composite coatings, and wear mechanisms of the coatings were discussed on the basis of the observation. The results obtained from MLS- 225 wet sand/rubber wheel test showed that the abrasive wear resistance of composite coatings with Cr 3 C 2 hard phase is about 28 times higher than that of Q235 mild steel. The coating method was proved effective in producing a uniform and dense lamellar structure. The excellent abrasive resistance of the composite coatings with Cr 3 C 2 particles were found to be related to three major factors: enhanced bulk hardness, compact lamellar structure and strong bonding between matrix and hard phase, as well as a load supporting system constructed by the hard phase structure.

Iron base composite coatings were deposited on mild steel substrates by arc spraying and cored wire with TiC ceramic powders. The abrasive wear resistance properties were examined on the MLS-225 wet sand/rubber wheel tester. The microstructure, phase compositions and worn surface morphologies of the coatings were observed by means of optical, scanning electron microscopy and X-ray diffraction. The results showed that composite coatings with TiC ceramic hard phases were reinforced by the TiC hard particles distributed in the iron-based coating. The average micro hardness of the coatings is about 1137 HV0.1. The coatings have the excellent abrasive wear resistance which is 6 times higher than that of the Q235 mild steel. Wear mechanisms of coatings was mainly micro-ploughing and brittle fracture.