Assessment of corrosion-induced changes on the mechanical integrity of cemented carbides at small length scales

Corrosion-induced changes on Hertzian contact damage in cemented carbides

“…Indentation stress-strain response seems to significantly depend on the depth of the corrosion affected zone. From a physical viewpoint, the degraded load-bearing capability evidenced must be attributed to the generation of porous/binderless corroded layers after corrosive exposure [28][29][30][31], as shown in Figure 5. In this regard, based on recent findings reported by the authors for sharp indentation and scratch testing of corroded hardmetals [31], the degraded layer is not expected to play a significant role in the plastic yielding onset until its thickness reaches a certain value.…”

“…Moreover, micrometric cavities are often evidenced, as a result of carbides dislodged during the contact load test. Hence, required accommodation of the imposed irreversible deformation results in deformation of single WC grains, particle cracking and fragmentation, as well as small-scale local collapse of the unsupported (binderless and porous) carbide network [30].…”

“…On one hand, leached binder J o u r n a l P r e -p r o o f leaves effective pores which may act as stress concentrators and crack precursors within binderless WC skeleton. On the other one, lack of binder implies that toughening mechanisms associated with ductile ligament reinforcement are now completely absent; and thus, energy required for subcritical crack propagation is effectively much lower than for the pristine condition [30][31][32]. Hence, induced microcracks may lead to catastrophic failure of the specimen as they propagate, interact and finally coalesce to form long cracks [31][32][33]50,52,69,70].…”

“…Refs. [25][26][27][28][29][30]. A quite interesting outcome from these studies is the detailed understanding acquired on the damage mechanisms at the micro-and nanometric dimensions: cracking, fragmentation and easy removal of WC grains under (sliding) contact, directly associated with the mechanically unsupported, contiguous and binderless/porous carbide network left after J o u r n a l P r e -p r o o f exposure to corrosive media of the studied hardmetals.…”

Indentation and scratch testing of a WC-6%wtCo cemented carbide: Corrosion effects on load-bearing capability and induced damage

“…Among their interesting observations, the evidence of structural collapse at the subsurface level together with irregular longitudinal scratch profiles, as a direct consequence of binder leaching, must be highlighted. A similar approach has been recently followed by Zheng et al [24] to assess and analyze surface/subsurface and small-scale mechanical integrity changes induced by exposure to an acidic media of a hardmetal grade. Such study included nanoindentation and nanoscratch testing together with inspection by means of Field Emission Scanning Electron Microscopy (FESEM).…”