Electroless Plating of Ni Nanoparticles on WC to Assist Its Pressureless Sintering of WC-Ni Cemented Carbide with Enhanced Mechanical and Corrosion-resistant Performance

Ni nanoparticles were coated uniformly on the surface of WC powder via a facile electroless plating method(abbreviated as WCN-EP),and then consolidated for mechanical and corrosion resistance performance characterization,in comparison with hand mixed WC-Ni(WCN-H).Under the optimized electroless plating parameters,Ni particles,less than 1μm in average diameter,were found to be uniformly and densely wrapped on the surface of the tungsten carbide matrix of WCN-EP.In comparison,in WCN-H,the Ni particles about 1.8μm in average diameter,were randomly distributed together with irregular WC particles.The uniform coating of Ni was found to assist the densification process of WCN-EP effectively,with higher densities and less pores than those of WCN-H at the Ni content of 10.6wt%,25.5wt%,and 30.3 wt%.However,at the Ni content of 18.8wt%,the relative densities of WCN-EP and WCN-H both increased to the maximum value of 98%.The maximum hardness of the consolidated WCN-EP was 82.6 HRA,about 1.2 HRA higher than that of WCN-H.In addition,the consolidated WCN-EP also exhibits a superior corrosion resistance by the polarization curve analysis at an electrochemical workstation.

Characterization and in-situ formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

The precursor carbonization method was first applied to prepare W–C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W–C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M7C3 carbides. Moreover, net-like structures were confirmed as mixtures of M23C6 and α-Fe; these structures were transformed from M7C3. The coarse herringbone M6C carbides did not only derive from the decomposition of M7C3 but also partly originated from the chemical reaction at the α-Fe/M23C6 interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M7C3 → M23C6 ＋ M6C.

Surface Features and Friction Characteristics of Porous and Coarse-grain WC-3%Co

The main components of cemented carbides include tungsten carbide(WC) and cobalt(Co),of which their melting point and density vary widely.It is not suitable for preparing porous cemented carbides according to the preparation process of the ordinary porous metal.In the paper,the porous cemented carbide was prepared with coarse-grain and low-cobalt alloy by modifying its sintering process.The surface features were observed through the metallurgical microscope,scanning electron microscope and three-dimensional profile instrument.The friction characteristics of WC/GCr15 sliding couplings under the dry condition were evaluated with the adoption of a ball-on-disk tribometer.The experimental results show that the porosity of porous cemented carbides varies from 7.5%to 9.0%.Their density and hardness decrease slightly.The size and depth of pits on their surfaces of porous cemented carbides are not quite uniform,namely,the depth ranges from several microns to 32 urn,which can be used to store the particles.The friction coefficient of porous cemented carbides is lower than the dense ones,and the wear resistance accordingly increases.It can be indicated that porous structure may have exerted an important influence on the dry friction properties of cemented carbides.