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1 Zeszyty Naukowe. Mechanika / Politechnika Opolska

1 2007

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Evaluation of cracks profile under the Vickers indentation

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Blažková K. , Jonšta Z. , Mazanec K.

2007

tom Vol. 321, z. 89

85-86

This work is devoted to the investigation of indentation crack profiles under Vickers indentation on two types cutting tool ceramics. First type of ceramics was aluminium oxide with zirconium oxide and the second one was silicon nitride ceramics. Vickers indents are created into the ceramic surface by hardness testing machine with a load of 294 N, loading time of indentations is 10 s. The value of investigated ceramics A12O3 + ZrO2 is equal to 1765 HV and Si3N4 ceramics reaches the average hardness value of 1574 HV. After Vickers indentation a system of initiated cracks and deformed area are initiated. The attention of this work is given up to the experimental technique by using serial sectioning to obtain depth profile of indentation cracks. By using this method it is possible to obtain a complete system of crack profiles under the Vickers indent and shape of deformed area. Serial sectioning methods are consisted of removing thin layers of material by ceramographic polishing. For each layer three polishing steps with diamond suspension 6,3 and 1 nm were performed. Two different processes of removing material method layer-by-layer are used. The first method consists in obtaining depth profile of the crack determined by ablating in steps from the surface into which the indentations was made. Diagonals of Vickers indents are measured before consecutive polishing and between every polishing step. In the case where the indents are already ablated there is no way how to determine the depth of polishing. To prevent to lose the depth reference new indents have to be created into the specimen surface before ablating previous ones, The second technique is based on layer removal from plane perpendicular to the indented surface. According the results the second method is more precise because of easier control of removed material, obtaining real profile of cracks system and deformed area under the Vickers indent.