Abstract
Purpose – This paper aims to carry out tribological experiments to explore the applications of femtosecond laser surface texturing technology on rock bit sliding bearing to enhance the lifetime and working performance of rock bit sliding bearing under high temperature and heavy load conditions. Design/methodology/approach – Surface textures on beryllium bronze specimen were fabricated by femtosecond laser ablation (800 nm wavelength, 40 fs pulse duration, 1 kHz pulse repetition frequency), and then the tribological behaviors of pin-on-disc configuration of rock bit bearing were performed with 20CrNiMo/beryllium bronze tribo-pairs under non-Newtonian lubrication of rock bit grease. Findings – The results showed that the surface texture on beryllium bronze specimens with specific geometrical features can be achieved by optimizing femtosecond laser processing via adjusting laser peak power and exposure time; more than 52 per cent of friction reduction was obtained from surface texture with a depth-to-diameter ratio of 0.165 and area ratio of 5 per cent at a shear rate of 1301 s−1 under the heavy load of 20 MPa and high temperature of 120°C, and the lubrication regime of rock bit bearing unit tribo-pairs was improved from boundary to mixed lubrication, which indicated that femtosecond laser ablation technique showed great potential in promoting service life and working performance of rock bit bearing. Originality/value – Femtosecond laser-irradiated surface texture has the potential possibility for application in rock bit sliding bearing to improve the lubrication performance. Because proper micro dimples showed good lubrication and wear resistance performance for unit tribo-pairs of rock bit sliding bearing under high temperature, heavy load and non-Newtonian lubrication conditions, which is very important to improve the efficiency of breaking rock and accelerate the development of deep-water oil and gas resources.
Highlights
Tribological properties of rock bit sliding bearings have crucial influences on the service life of rock bit
The purpose of this paper is to explore the application of fs laser surface texturing on mating components of rock bit sliding bearings, by focusing on the effects of fs laser power and pulse numbers on geometrical characteristics of the surface textures, and comparing the tribological behavior of textured surface and un-textured surfaces in high temperature, heavy load and non-Newtonian lubrication conditions
An effective laser texturing processing on beryllium bronze disc specimens of rock bit bearing was achieved by using a fs laser
Summary
Tribological properties of rock bit sliding bearings have crucial influences on the service life of rock bit. Heavy load and harsh lubrication conditions, the early stage damage of sliding bearing was accounted for 80 per cent of rock bit total failure (Wu and Ma, 1998). The failure form of tribo-pairs of rock bit sliding bearing, which were respectively made of 20CrNiMo and beryllium bronze, was mainly adhesive wear (Wang et al, 2006). The tribological behavior of 20CrNiMo/beryllium bronze has become one significant guideline estimating the life of rock bit sliding. Its performance directly influences drilling costs and efficiency (Wang and Liu, 2012). Reduction of friction is considered to be a necessary requirement for
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