Simultaneous abrasion and edge fracture resistance estimation of hard materials by the tribotesting method

• Autorzy: Ścieszka S. F.

Warianty tytułu

PL

Tribologiczna metoda łącznego wyznaczania odporności na zużycie ścierne i pękanie krawędziowe dla materiałów ceramicznych i węglików spiekanych

• Języki publikacji: EN

Abstrakty

EN

Fracture toughness and wear resistance are two of the major material characteristics to take into consideration when designing tools, particularly inserts for rotary and percussion rotary drilling, inserts for mining shearer picks and rotary picks made of hardmetals (WC-Co cemented carbides). This is mainly due to the high risk of brittle fracture in tools made of these materials and due to the importance of resistance to abrasion where the contact pressure between the component and abrasive is high as in mining and rock drilling. WC-Co hardmetals are materials that combine high abrasion resistance and hardness with rather low levels of toughness as a consequence of their microstructure. Nevertheless, the main problem facing designers remains the fact that the tungsten carbide and other cermetal tools may exhibit sudden brittle fracture. Since fracture toughness is often the major limiting parameter governing the use of WC-Co drilling and cutting tools, there is a need for research aimed at increasing toughness without sacrificing wear resistance. To aid in this objective, a simple and reliable integrated testing method, such as that presented in this paper, is needed for quick assessment of progress in such research. There are several methods for the measurement of fracture toughness, although there is no standard method for hardmetals. The single edge pre-cracked beam method and the chevron notch method (both proposed by the ASTM) are most commonly used despite the fact that they are rather expensive and laborious. Problems connected with the effective and reliable use of these experimental methods has stimulated efforts towards the following: firstly, the development of empirical and semi-empirical formulae describing the relationship between the critical stress intensity factor (KIC) and other mechanical and physical properties that are much easier to evaluate; and, secondly, the development of new toughness evaluation methods based on edge damage pattern. One such method currently evolved by the Tribotechnology Division at Silesian University of Technology is the subject of further, more advanced study together with the Institute for Sustainable Technologies, Radom. The method is based on the concept of edge chipping in the initial transition stage of abrasion wear, which is controlled by the brittle fracture process. The method of testing is seen as a promising and pragmatic way of ranking hard materials for fracture toughness and wear resistance. The limitations of the method for tougher materials such as novel hardmetals and ceramics are investigated in this paper.

PL

Odporność na pękanie i odporność na zużycie ścierne są dwoma głównymi parametrami charakteryzującymi materiały stosowane na narzędzia, takie jak np. wiertła, noże kombajnów ścianowych i chodnikowych. Ostrza tych narzędzi wykonuje się obecnie głównie z węglików spiekanych (WC-Co). Znaczenie ww. parametrów jest konsekwencją udziału dwóch głównych mechanizmów uszkodzeń prowadzących do utraty zdatności eksploatacyjnej tych narzędzi, czyli pękania ostrzy oraz ich zużycia ściernego w kontakcie ze skałą w trakcie wiercenia lub urabiania przez skrawanie. Ponieważ odporność na pękanie i zużycie ścierne decydują o właściwym doborze materiałów na ostrza narzędzi, potrzebna jest do oceny tych materiałów metoda badawcza integrująca oba główne mechanizmy uszkodzeń. Metodę taką oraz jej praktyczne zastosowanie przedstawiono w tym artykule. Znanych jest kilka metod pomiaru odporności na kruche pękanie, chociaż żadna z nich nie została uznana za standardową dla węglików spiekanych. Stosowana jest np. metoda SEPB (Single Edge Pre-cracked Beam) oraz metoda CNB (Chevron Notched Beam), chociaż obie te metody są raczej pracochłonne dla materiałów kruchych. Trudności związane z efektywnym i niezawodnym zastosowaniem dla twardych i kruchych materiałów eksperymentalnego wyznaczania odporności na pękanie (KIC) w warunkach płaskiego stanu odkształcenia spowodowały poszukiwanie metod alternatywnych. Jedna z takich metod, obecnie opracowywana w Politechnice Śląskiej, jest przedmiotem dalszych badań rozwojowych razem z Instytutem Technologii Eksploatacji w Radomiu. W tym artykule są przedstawione wstępne wyniki tej pracy oraz wcześniejsze badania własne autora.

Słowa kluczowe

EN

abrasion; fracture toughness; tungsten carbide; tribotester

PL

zużycie ścierne; odporność na pękanie; węglik spiekany; tribotester

• Wydawca: Wydawnictwo Naukowe Instytutu Technologii Eksploatacji - Państwowego Instytutu Badawczego
• Czasopismo: Scientific Problems of Machines Operation and Maintenance
• Rocznik: 2011
• Tom: Vol. 46, nr 2
• Strony: 55--104
• Opis fizyczny: Bibliogr. 57 poz., fot., rys., tab.

Twórcy

autor

Ścieszka S. F.

• Silesian University of Technology, Faculty of Mining and Geology, Institute of Mining Mechanisation, Akademicka 2 Street, 44-100 Gliwice, Poland,

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