Nonlinear Wear Response of WC-Ni Cemented Carbides Irradiated by High-Intensity Pulsed Ion Beam

Abstract

Surface hardening on WC-Ni cemented carbides was achieved by high-intensity pulsed ion beam (HIPIB) irradiation, with formation of a binderless, densified, and “hilly” remelted top layer of a few μm in depth and a shock strengthened underlayer down to a hundred μm. The tribological behavior of the samples was studied under dry sliding against GCr15 bearing steel on a block-on-ring tribometer with 98 N and 0.47 m/s. The specific wear rate/wear resistance presented an exponential dependence on the surface hardness, in contrast to the commonly reported linear dependence of the specific wear rate or wear resistance on the hardness of WC based cemented carbides among both WC-Ni and WC-Co systems. The original samples underwent a severe abrasive wear due to the Ni binder micro-abrasion and WC grain fragmentation/pullout, whereas the irradiated samples began with a gradual abrasion of the binderless hard tops, followed by a mild abrasive wear accompanied by local adhesive wear. The wear resistance has been also compared with the reported data concerning the relative hardness of friction pairs in a value range of 2–7 on block-on-ring tribometer tests with the friction pairs of WC cemented carbides and steels in unlubricated condition. The nonlinear wear response is explained by the wear mechanism transition otherwise unobtainable in the case of the reported hardening by either lowering the binder content or refining the WC grains. It is revealed that the interfacial bonding enhancement of the WC/binder and the binder strengthening are pronounced for improving the wear resistance of the cemented carbides, by the effective suppressing of the WC grain fragmentation/pullout and binder micro-abrasion, even though they have limited contribution to the hardness enhancement.

Water-lubricated tribological behavior of WC-Ni coatings deposited by off-angle HVOF spraying

“…It is shown that, all the coatings mainly underwent a mild abrasive wear process with some small and shallow parallel ploughing scratches presented on the surface. This wear morphology is similar to that of bulk WC-Ni mild abrasive wear accompanied with some adhesive wear under dry sliding against a softer bearing steel wear pair in our previous study [21]. Note that, in the present study, much more mild abrasive wear is obtained with a low specific wear rate 1 order less due to well water lubricated condition.…”

“…As a result, the deterioration effect of the slight reduction in the mechanical properties on wear resistance could be compensated by the improved lubrication leading to a lower friction force at the interface in comparison with that of normal spray angle. In our previous study for wear resistance on surface modified bulk WC-Ni cemented carbide under unlubricated condition, it is revealed that the abrasive wear of WC-Ni originates from generation of pull-off carbide particles or fragmentation on the friction interface, while adhesive wear from the preferential removal of metallic binder phase under deformation and protrusion from between the much harder carbide phase [21].…”