INFLUÊNCIA DO DESGASTE DA ESFERA NA FORMAÇÃO DAS CRATERAS DE DESGASTE EM ENSAIOS BALL-CRATERING
BALL WEAR INFLUENCE AT THE CAPS FORMATION IN THE MICRO‑ABRASIVE WEAR TESTING BY BALL-CRATERING
Cozza, Ronaldo Câmara
http://dx.doi.org/10.4322/2176-1523.0828
Tecnol. Metal. Mater. Min., vol.12, n3, p.202-210, 2015
Resumo
Surgido no setor industrial, o ensaio de desgaste micro-abrasivo por esfera rotativa difundiu-se rapidamente no meio acadêmico, sendo utilizado em diversas pesquisas envolvendo desgaste abrasivo de materiais. Entretanto, um assunto pouco discutido entre os pesquisadores é o desgaste da esfera, que, dependendo da configuração do equipamento, pode fazer com que as calotas geradas apresentem contornos que divergem ao formato circunferencial. Consequentemente, essa imperfeição ocasionará erros quando forem calculados, além do próprio diâmetro, a altura e o volume da cratera de desgaste. Este trabalho apresenta um estudo sobre a influência do desgaste da esfera na formação das crateras de desgaste em ensaios de desgaste micro-abrasivo por esfera rotativa fixa. Foram utilizados corpos-de-prova de aço-ferramenta (HSS) M2, metal duro (WC-Co) classe P20 e uma esfera de aço AISI 52100. A lama abrasiva foi preparada com carbeto de silício (SiC) preto (com tamanho médio de partícula de 5 μm) e água destilada. Durante os ensaios, a pasta abrasiva foi inserida de maneira intermitente entre o corpo-de-prova e a esfera, através de um conta-gotas. As crateras de desgaste foram analisadas por meio de um microscópio óptico, com a finalidade de verificar seus contornos. Foi observado que, até um determinado grau de desgaste apresentado pela linha de trabalho da esfera de ensaio, os contornos das calotas esféricas tendiam a uma circunferência. Conforme o desgaste da esfera foi aumentando, os contornos apresentaram formatos denominados “elíptico”, “oblongo” e “8”. Além disso, com o aumento do nível de desgaste da esfera de ensaio, relatou-se um aumento do desvio-padrão dos valores dos diâmetros das crateras de desgaste.
Palavras-chave
Ball-cratering wear test, Desgaste abrasivo, Desgaste da esfera.
Abstract
The micro-abrasive wear testing by rotating ball appeared in the industrial sector and quickly spread to academic institutions, where it has been used in many studies on the micro-abrasive wear of materials. However, ball wear is an issue that has received only little attention. Depending on equipment configuration, ball wear can result in craters with boundaries different from circumferential. Consequently, this imperfection will cause errors during the calculation, besides the diameter itself, on the height and the volume of the crater. This work presents a study on the influence of ball wear on crater formation in the micro-abrasive wear testing with fix ball. Tests were conducted with HSS M2 and WC-Co P20 specimens and one ball of AISI 52100 steel. The slurry was prepared with black silicon carbide (SiC) (with mean particle size of 5 μm) and distilled water. During the tests, the slurry was supplied intermittently between the specimen and the ball, by a dropper. The craters were analyzed by optical microscopy, in order to verify their boundaries. It was observed that, until a given wear level of the ball, the boundaries of craters tended to a circumference. When the ball wear level increased, the boundaries presented tendency for contours called “elliptical”, “oblong” and “8” (“eight”). Besides, with the increase of the ball wear level, it was reported an increase of the standard deviation of the diameters values of the wear craters.
Keywords
Ball-cratering wear test, Abrasive wear, Ball wear.
Referências
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2. Cozza RC, Tanaka DK, Souza RM. Friction coefficient and abrasive wear modes in ball-cratering tests conducted at constant normal force and constant pressure – Preliminary results. Wear. 2009;267(1-4):61-70. http://dx.doi. org/10.1016/j.wear.2009.01.055.
3. Trezona RI, Allsopp DN, Hutchings IM. Transitions between two-body and three-body abrasive wear: influence of test conditions in the microscale abrasive wear test. Wear. 1999;225-229:205-214. http://dx.doi.org/10.1016/S00431648(98)00358-5.
4. Batista JCA, Matthews A, Godoy C. Micro-abrasive wear of PVD duplex and single-layered coatings. Surface and Coatings Technology. 2001;142-144:1137-1143. http://dx.doi.org/10.1016/S0257-8972(01)01189-6.
5. Batista JCA, Godoy C, Matthews A. Micro-scale abrasive wear testing of duplex and non-duplex (single-layered) PVD (Ti,Al)N, TiN and Cr-N coatings. Tribology International. 2002;35(6):363-372. http://dx.doi.org/10.1016/ S0301-679X(02)00017-8.
6. Cozza RC. A study on friction coefficient and wear coefficient of coated systems submitted to micro-scale abrasion tests. Surface and Coatings Technology. 2013;215:224-233. http://dx.doi.org/10.1016/j.surfcoat.2012.06.088.
7. Cozza RC. Effect of pressure on abrasive wear mode transitions in micro-abrasive wear tests of WC-Co P20. Tribology International. 2013;57:266-271. http://dx.doi.org/10.1016/j.triboint.2012.06.028.
8. Adachi K, Hutchings IM. Wear-mode mapping for the micro-scale abrasion test. Wear. 2003;255(1-6):23-29. http:// dx.doi.org/10.1016/S0043-1648(03)00073-5.
9. Adachi K, Hutchings IM. Sensitivity of wear rates in the micro-scale abrasion test to test conditions and material hardness. Wear. 2005;258(1-4):318-321. http://dx.doi.org/10.1016/j.wear.2004.02.016.
10. Cozza RC. Estudo do comportamento do coeficiente de desgaste e dos modos de desgaste abrasivo em ensaios de desgaste micro-abrasivo [dissertação de mestrado]. São Paulo: Universidade de São Paulo; 2006 [acesso em 22 jul. 2014]. Disponível em: http://www.teses.usp.br/.
11. Ramalho A. Micro-scale abrasive wear of coated surfaces-prediction models. Surface and Coatings Technology. 2005;197(2-3):358-366. http://dx.doi.org/10.1016/j.surfcoat.2004.12.024.
2. Cozza RC, Tanaka DK, Souza RM. Friction coefficient and abrasive wear modes in ball-cratering tests conducted at constant normal force and constant pressure – Preliminary results. Wear. 2009;267(1-4):61-70. http://dx.doi. org/10.1016/j.wear.2009.01.055.
3. Trezona RI, Allsopp DN, Hutchings IM. Transitions between two-body and three-body abrasive wear: influence of test conditions in the microscale abrasive wear test. Wear. 1999;225-229:205-214. http://dx.doi.org/10.1016/S00431648(98)00358-5.
4. Batista JCA, Matthews A, Godoy C. Micro-abrasive wear of PVD duplex and single-layered coatings. Surface and Coatings Technology. 2001;142-144:1137-1143. http://dx.doi.org/10.1016/S0257-8972(01)01189-6.
5. Batista JCA, Godoy C, Matthews A. Micro-scale abrasive wear testing of duplex and non-duplex (single-layered) PVD (Ti,Al)N, TiN and Cr-N coatings. Tribology International. 2002;35(6):363-372. http://dx.doi.org/10.1016/ S0301-679X(02)00017-8.
6. Cozza RC. A study on friction coefficient and wear coefficient of coated systems submitted to micro-scale abrasion tests. Surface and Coatings Technology. 2013;215:224-233. http://dx.doi.org/10.1016/j.surfcoat.2012.06.088.
7. Cozza RC. Effect of pressure on abrasive wear mode transitions in micro-abrasive wear tests of WC-Co P20. Tribology International. 2013;57:266-271. http://dx.doi.org/10.1016/j.triboint.2012.06.028.
8. Adachi K, Hutchings IM. Wear-mode mapping for the micro-scale abrasion test. Wear. 2003;255(1-6):23-29. http:// dx.doi.org/10.1016/S0043-1648(03)00073-5.
9. Adachi K, Hutchings IM. Sensitivity of wear rates in the micro-scale abrasion test to test conditions and material hardness. Wear. 2005;258(1-4):318-321. http://dx.doi.org/10.1016/j.wear.2004.02.016.
10. Cozza RC. Estudo do comportamento do coeficiente de desgaste e dos modos de desgaste abrasivo em ensaios de desgaste micro-abrasivo [dissertação de mestrado]. São Paulo: Universidade de São Paulo; 2006 [acesso em 22 jul. 2014]. Disponível em: http://www.teses.usp.br/.
11. Ramalho A. Micro-scale abrasive wear of coated surfaces-prediction models. Surface and Coatings Technology. 2005;197(2-3):358-366. http://dx.doi.org/10.1016/j.surfcoat.2004.12.024.
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