| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1603635 | International Journal of Refractory Metals and Hard Materials | 2013 | 6 Pages |
Electrical discharge machining (EDM) provides an effective means of shaping hardmetals. However, it is also known that surface integrity of these materials may be affected by EDM, degrading their tribomechanical characteristics. This work focuses on assessing the use of two different surface modification routes: thermomechanical treatments (shot blasting, polishing and final high temperature annealing) and/or physical vapor deposition of hard coatings, for improving the fracture and fatigue strength of an EDM-shaped fine-grained hardmetal grade. In doing so, an optimal EDM's surface finish variant and a diamond ground and polished one are used. Mechanical behavior is evaluated under four-point bending and fatigue characterization is given in terms of fatigue limit following the staircase method. Experimental results indicate that both approaches markedly decrease the lessening effect of EDM on the mechanical strength of hardmetals, although a complete fracture and fatigue strength retention is only achieved by combining both of them. The improved mechanical behavior is rationalized on the basis of the beneficial changes induced by surface modification on the effective residual stress field at the surface of EDM-shaped hardmetals, as assessed by a linear elastic fracture mechanics analysis combined with fractographic examination.
► Suitable post-machining actions for mitigating strength degradation induced by EDM on hardmetals. ► Effectiveness of thermal annealing and coating deposition for enhancing fracture and fatigue strength of EDMed hardmetals. ► Implementation of LEFM concepts for rationalizing surface modification effects on the strength behavior of EDMed hardmetals. ► Description of EDM influence on the fatigue strength of hardmetals through mean stress effects on fatigue limit.
