On design and tribological behaviour of laser textured surfaces

The paper reports an investigation into the functional response of textured surfaces with different designs that incorporated arrays of micro-dimples and grooves (40 μm diameter/width and 15 μm depth for both patterns) produced on tungsten carbide (WC) blocks by employing nanosecond (ns) and femtosecond (fs) lasers. In particular, the tribological performance of the textured WC blocks against stainless steel (SS316L) counterbody was evaluated in terms of friction and wear under dry condition compared to an untextured specimen. Friction tests were carried out on a reciprocating sliding tester while unidirectional ball-on-disc method was utilised to assess wear on the mating surfaces. The untextured surface exhibited a continuous rise in the friction coefficient from 0.15 to 0.5 from the start of the cycle to the end while the specimens textured with ns and fs lasers reached steady-state condition after 100 and 200 cycles with values between 0.35-0.45 and 0.3-0.4, respectively. Energy dispersive spectroscopy following wear tests showed a pronounced material transfer from the balls to the textured surfaces with stainless steel filling up some of the dimple and groove cavities; however, the reverse phenomenon was not apparent. Additionally, texturing with the fs laser exhibited formation of nano-ripples/structures in the produced dimples and grooves that can be further studied for creating nano-textured cutting tools or surfaces with super-hydrophobic/anti-ice properties

Mechanical and Tribological Properties of PVD-Coated Cemented Carbide as Evaluated by a New Multipass Scratch-Testing Method

A new test method based on multipass scratch testing has been developed for evaluating the mechanical and tribological properties of thin, hard coatings. The proposed test method uses a pin-on-disc tribometer and during testing a Rockwell C diamond stylus is used as the “pin” and loaded against the rotating coated sample. The influence of normal load on the number of cycles to coating damage is investigated and the resulting coating damage mechanisms are evaluated by posttest scanning electron microscopy. The present study presents the test method by evaluating the performance of Ti0.86Si0.14N, Ti0.34Al0.66N, and (Al0.7Cr0.3)2O3 coatings deposited by cathodic arc evaporation on cemented carbide inserts. The results show that the test method is quick, simple, and reproducible and can preferably be used to obtain relevant data concerning the fatigue, wear, chipping, and spalling characteristics of different coating-substrate composites. The test method can be used as a virtually nondestructive test and, for example, be used to evaluate the fatigue and wear resistance as well as the cohesive and adhesive interfacial strength of coated cemented carbide inserts prior to cutting tests

A custom built lathe designed for in operando high-energy x-ray studies at industrially relevant cutting parameters

We present a custom built lathe designed for in operando high-energy x-ray scattering studies of thetool-chip and tool-workpiece contact zones during operation. The lathe operates at industriallyrelevant cutting parameters, i.e. at cutting speeds ≤ 400 m/min and feeds ≤ 0.3 mm/rev. By turningtests in carbon steel, performed at the high-energy material science beamline P07 at Petra III, DESY,Hamburg, we observe compressive strains in TiNbAlN and Al2O3/Ti(C,N) coatings on the tool flank faceduring machining. It is demonstrated that by the right choice of substrate and coating materials,diffraction patterns can be recorded and evaluated in operando, both from the tool-workpiece andtool-chip contacts, i.e. from the contact zones between the tool and the workpiece material on thetool flank- and rake faces, respectively. We also observe that a worn tool results in higher temperaturein the tool-chip contact zone compared to a new tool.Thi

Resolving the debated atomic structure of the metastable cubic SiNx tissue phase in nanocomposites with TiN

The TiN/SiNx nanocomposite and nanolaminate systems are the archetype for super if not ultrahard materials. Yet, the nature of the SiNx tissue phase is debated. Here, we show by atomically resolved electron microscopy methods that SiNx is epitaxially stabilized in a NaCl structure on the adjacent TiN(001) surfaces. Additionally, electron energy loss spectroscopy, supported by first-principles density functional theory calculations infer that SiNx hosts Si vacancies.Funding Agencies|Swedish Research Council (VR) [2008-405, 2012-4359, 2015-04391, 2016-04412]; Swedish Foundation for Strategic Research (SSF) through FunCase; SRL [10-0026]; M. Bergwall foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005, K2-2017-080]; [RIF 14-0074]</p