The use of fracture mechanics for rationalizing the fracture behavior of cemented carbides is valid, as far as sharp cracks, free of residual stresses and subjected to a well-defined stress state are used for assessing fracture toughness. However, machining a very sharp notch on the surface of hardmetals for fracture toughness testing has been a critical issue during many years. Within this context, introduction of surface “through-thickness” micronotches (SEμVNB) by means of ultrashort pulsed laser ablation (UPLA) is here proposed, implemented and analyzed as an innovative precracking-like route within flexural testing procedures for appropiated evaluation of fracture toughness of cemented carbides. UPLA parameters used for introducing the micronotch are optimized in terms of induced damage ahead of the notch tip. For comparison purposes, fracture toughness is also determined by means of flexural testing of previously cracked single-edge notch beams (SENB-Cracked) as well as specimens with V-notch tips sharpened through diamond polishing using a razor blade, and Palmqvist indentation microfracture method. The satisfactory agreement found between values measured using UPLA-micronotched and SENB-Cracked (reference) specimens allows to conclude that flexural testing of SEμVNB samples is a valid methodology for reliable determination of fracture toughness of hardmetals. This is feasible because of the extremely short time of laser-matter interaction. It yields small and somehow controlled damage in front of the notch tip as a result of shock wave propagation during ablation, which translates into effective precracking of SEμVNB specimens.

使用断裂力学来合理化硬质合金的断裂行为是有效的，只要尖锐裂纹、无残余应力和受到明确定义的应力状态用于评估断裂韧性。然而，多年来，在硬质合金表面加工一个非常锋利的缺口以进行断裂韧性测试一直是一个关键问题。在此背景下，本文提出、实施和分析通过超短脉冲激光烧蚀 (UPLA) 引入表面“全厚度”微缺口 (SEμVNB) 作为弯曲测试程序中的一种创新的类似预裂的途径，以适当评估断裂韧性的硬质合金。用于引入微缺口的 UPLA 参数在缺口尖端之前的诱导损伤方面进行了优化。出于比较目的，断裂韧性还通过对先前破裂的单刃缺口梁 (SENB-Cracked) 以及通过使用剃刀刀片和 Palmqvist 压痕微断裂法进行金刚石抛光而锐化的 V 型缺口尖端的试样进行弯曲测试来确定。使用 UPLA 微缺口和 SENB 裂纹（参考）试样测量的值之间的令人满意的一致性可以得出结论，SEμVNB 样品的弯曲测试是可靠确定硬质合金断裂韧性的有效方法。这是可行的，因为激光与物质相互作用的时间极短。由于消融过程中的冲击波传播，它会在缺口尖端前产生小的且以某种方式受控的损伤，这转化为 SEμVNB 试样的有效预裂。