Microstructure and Tribological Properties of Plasma-sprayed WC-17 Co Coatings with Different Carbide Grain Size Distribution

Abstract

In the present work, three experimental WC-17 Co plasma sprayed coatings were developed from submicrostructured, conventional and bimodal (composing of 30 wt.% submicrostuctured and 70 wt.% conventional WC grain) agglomerated powder. The effect of carbide size distribution on the microstructure, phase structure and properties such as microhardness, fracture toughness and sliding wear performance of three coatings were measured. The experimental results indicated that bimodal coating had little porosity of microstructure with lower degree of decarburization of the WC phase to W 2 C and Co 6 W 6 C phases, consequently, showed both high microhardness and fracture toughness, e.g. the microhardness is similar to that of the submicrostuctured one and the fracture toughness is comparable to that of the conventional one. The coefficient of friction for the coatings decreased slightly with increasing test load, and that friction coefficient of bimodal coating was lower than the other ones. The wear loss of both submicrostuctured and conventional coatings were higher than the bimodal coating and increased with increasing test load. The microscopic analyses of the wear surface showed the cobalt extrusion followed by carbide fracture, or pulled out were the predominant failure mechanism. Besides that, fatigue cracking of the submicrostuctured coating at a high test load played an importance on the wear mechanism.

Development and Characterization of Natural Chromite Coating on Metal Substrate Using the Plasma Spray Process

“…Microhardness of fine particle coating is relatively higher than the coarse particles coating, as the coating is more compact due to the slightly lower porosity value than its counterpart. 43 Voids and pores are present in both type of coatings and are clearly marked in coating top surface images (Figure 5a,b. The voids may be formed either due to the combination of some porosities or due to the shrinkage upon solidification (Figure 5b).…”

“…Coatings exhibited higher hardness than the substrate material. Microhardness of fine particle coating is relatively higher than the coarse particles coating, as the coating is more compact due to the slightly lower porosity value than its counterpart …”

Effects and Interplays of Spray Angle and Stand-off Distance on the Sliding Wear Behavior of HVOF WC-17Co Coatings

“…However, the effect of tribofilm to the wear behavior of cermet coatings is still unclear. Certain authors support that it has lubricating properties that stem from the presence of certain oxides that are generated from the heat of friction (Ref [34][35][36] and contributes to lowering the COF, while others (Ref 37,38) demonstrate that COF is, in fact, elevated in the presence of tribofilm.…”

Operational tests of coating systems in military technology applications

“…Currently, there is a dynamic development of coating production processes using various surface engineering technologies, such as: plasma spraying [39], HVOF spraying [40], ESD method [33], laser cladding [43], laser alloying [32], physical vapor deposition [12], chemical vapor deposition [8], which mainly perform protective and anti-wear functions.…”