Wear and friction of TiAlN/VN coatings against Al2O3 in air at room and elevated temperatures

Abstract

TiAlN/VN multilayer coatings exhibit excellent dry sliding wear resistance and low friction coefficient, reported to be associated with the formation of self-lubricating V2O5. To investigate this hypothesis, dry sliding ball-on-disc wear tests of TiAlN/VN coatings on flat stainless steel substrates were undertaken against Al2O3 at 25 0 C, 300 0 C and 635 0 C in air. The coating exhibited increased wear rate with temperature. The friction coefficient was 0.53 at 25 0 C, which increased to 1.03 at 300 0 C and decreased to 0.46 at 635 0 C. Detailed investigation of the worn surfaces was undertaken using site-specific transmission electron microscopy (TEM) via focused ion beam (FIB) microscopy, along with Fourier transform infrared (FTIR) and Raman spectroscopy. Microstructure and triboinduced chemical reactions at these temperatures were correlated with the coating's wear and friction behaviour. The friction behaviour at room temperature is attributed to the presence of a thin hydrated tribofilm and the presence of V2O5 at high temperature.

Temperature dependent friction and wear of magnetron sputtered coating TiAlN/VN

“…For TiAlN/VN coatings, high temperature tribo-tests have been undertaken on limited temperatures, e.g. 500 0 C and 700 0 C in [18] and 300 0 C and 630 0 C in [21]. Surprisingly high friction coefficients of µ = ~0.95 were reported at 300 0 C and 500 0 C. Especially, comprehensive worn surface analyses have updated previous understanding regarding the lubricious effect of V 2 O 5 type wear debris.However, while the limited studies indicated remarkable different friction behaviours at different temperatures, it is not still not clear at least in the following aspects: (1) how the friction coefficient of TiAlN/VN changes with varying temperature; (2) the effect of friction coefficient on the wear rate; and (3) relationship between wear, oxidation and friction at elevated temperatures especially when the TiAlN/VN has been found to oxidise at temperatures higher than 550 0 C [27].…”

“…Instead, they are response of sliding surfaces under the applied test conditions. According to published experimental studies [12][13][14][15][16][17][18][19][20][21], environment temperature has significant influence on the sliding friction and wear behaviour of transition metal nitrides. For example, a Cl-containing TiN coating grown by chemical vapour deposition showed extraordinarily low friction of µ < 0.2 and high friction of µ = 0.6 -0.8 at 100 -300 0 C [17].…”

Tribofilms in Solid Lubricants

“…But more importantly, tribo-heating at the sliding interface triggered chemical reactions between the adsorbents and the wear debris. In this case, the tribofilms and wear debris contained both multi-component oxides and hydroxides, which have been confirmed by EDX, EELS, Raman and FTIR analyses [7] . As an example, Figure 5 shows the electron energy loss spectrum of the tribofilm shown in Figure 4 as compared to the spectrum of the underneath TiAlN/VN, suggestive of tribo-oxidation in the former.…”

Mecanizado de Acero AISI1020, Utilizando Buriles con Recubrimiento Monocapa de Nitruro de Vanadio

“…Al analizar comparativamente el estado de ambas herramientas, se manifiesta mayor desgaste y disminución del filo de la herramienta comercial, figura 5a, presentando a 14,7 m de mecanizado un desgaste de flanco de 0,1 mm en el buril comercial y de 0,06 mm en el buril recubierto; evidenciado en el desprendimiento del material, generado en la superficie de incidencia de la herramienta y es ocasionado por frotamiento de la herramienta sobre la superficie mecanizada y a las temperaturas de trabajo (Álvarez, 2009). La mayor resistencia frente al desgaste luego del proceso de mecanizado se presentó en el buril recubierto con VN, figura 5b; esta característica del puede atribuirse a la formación de óxido de Vanadio, la cual actúa como lubricante entre las partes en contacto disminuyendo el coeficiente de fricción y a su vez el desgaste (Qiu, Li, et al, 2013), disminuyendo la probabilidad de presentar mecanismos de desgaste en la herramienta (Zhoua et al, 2010). En la Fig.…”