In this work, in order to find a reasonable replacement material for WC-Co coatings, high carbon ferrochromium, low carbon ferrochromium and high carbon ferrochromium-nickel composite coatings were selected and their characterization and wear behaviour were studied. The coatings were applied on plain carbon steel by air plasma spray. Ferrochromium coatings were sprayed with different argon gas flow rates and subsequently they were compared with each other. The results indicated that the coatings with the lower argon gas flow rate had better properties due to longer thermal stability at high tempreture. To investigate the mechanical and wear properties, high carbon ferrochromium was choosen as the ferrochromium-nickel composite coatings. Ni was selected as the binder to improve the binding between the ferrochromium particulates. Composite coatings with different amounts of nickel 10, 20 and 30 weight percent were produced. At the begining high carbon ferrochromium and nickel were mixed by using ring grinding, prepared under control atmosphere, consequently the materials sintered and crushed into suitable partilce size for flowability in the thermal spray equipment. Images of scanning electron microscopy showed, a uniform distribution of nickel through coatings therefore a metal matrix composite coating was truely made. Composite coatings had different mechanical and wear behaviour. In comparing with ferrochromium coatings, fracture toughness values of composite coatings were increased. HCFeCr-10%Ni had the weakest properties between all coatings, so it showed that, this percentage of nickel wasn`t adequate as binder in coating, and it couldn`t make a good cohesion between ferrochromium particles, also it caused high percentage of porosity. HCFeCr-20%Ni had the best mechanical and wear behaviour. With adding 20%Ni to HCFeCr, microhadrness value increased from 763 to 950 Vickers and also fracture toughness values increased from 1.9 to 4.5 MPa?m. The dominant wear mechanism in HCFeCr and composite coatings was identified as adhesive wear with microcracking with different severity. It is found that delamination mechanism was the predominant wear mechanism for LCFeCr coating. Furtherrmore HCFeCr-20% Ni composite coating showed an optimum behaviour and the lowest value of weight loss. HCFeCr-10%Ni coating showed the highest weight loss among all the coatings. Therefore the HCFeCr-20%Ni was selected as the most promising coating and it could be a better replacement for the expensive WC-Co coatings. Keywords: Composite coating, Ferrochromium, Nickel, Air Plasma Spray, Wear
