Research Of Preparation Of WC-12Co-3Al Coating And Its Structural Properties

Sub-micronstructured WC-12Co coatings by High Velocity Oxygen-Fuel (HVOF)spraying are widely used in various applications, with high hardness and excellentwear resistance. However, the weakness of sub-micronstructured WC-12Co coatingsis its binders which are easy to be removed. In consequence, in order to enhancewear-resistance of coating, strength of binders must be improved. By high energy ballmilling, Al powders are added into nanostructured WC-12Co powders as a new kindof alloy powders. These powders are deposited into coating by HVOF.Elemental Al completely resolved into bonding layer of powders though50h highenergy ball-milling. Select powders with suitable particle size after ball-milling. Thenobtain the coating by high velocity oxygen fuel spray technology. Obtain tribologicalbehavior of WC-Co-Al coatings through frictional experiment and observe themicrostructure by SEM and XRD etc.In the case of submicron-sized WC-Co coating, wear is caused by an initialremoval of the binder phase followed by a fragmentation or uprooting of carbideparticles. As a consequence of that, the wear debris became trapped between thecoating and counter body, and cause further damage in the coating as frettingcontinues. The wear mechanism in the case of nanostructured WC-Co coating with orwithout Al alloying, appears to be surface fracture, followed by a gradual removal ofWC and Co particles from the coating. The Al addition in the metallic matrixenhanced the particle uprooting as fretting continues.The bonding layer of WC-12Co-3Al coating are strengthened by solutionstrengthening and second phase strengthening to protect Co and WC from removing.WC-12Co coatings, whether contain Al or not, will oxidate above500℃. WCoO4phase are generated in the coating if oxygen involved. If protected in inert atmosphere,η phase are generated.