Thermal stability of a laser-clad NiCrBSi coating hardened by frictional finishing

Frictional treatment decreases surface roughness of a NiCrBSi laser coating and increases its microhardness and abrasive wear resistance. Even after softening annealing at 900 °C, the coating subjected to frictional treatment preserves its advantage in hardness and wear resistance over the original clad coating. Annealing at 1000 °C after frictional treatment ensures less effective growth of the hardness and wear resistance of the coating as compared to annealing of the undeformed coating due to the limited precipitation of large Cr23C6 carbides on the deformed surface, which form a wear-resistant framework. © 2017 Author(s).Russian Foundation for Basic Research, RFBR: 16-38-00452-mol-a01201375904108692015Federal Agency for Scientific Organizations: 01201463331Federal Agency for Scientific OrganizationsUral Branch, Russian Academy of Sciences, UB RAS: 15-9-12-45The study was financially supported by the Russian Foundation for Basic Research (RFBR), grant No. 16-38-00452-mol-a, by the Foundation for Assistance to Small Innovative Enterprises (FASIE), project UMNIK No. 108692015; the work was done within the Complex Program of UB RAS, project No. 15-9-12-45, within the state order for IES UB RAS, No. 01201375904 and within the state order of The Federal Agency for Scientific Organizations (FASO Russia) on the subject “Structure”, No. 01201463331. The experimental research was done on the equipment installed at the Plastometriya Collective Use Center of IES UB RAS

Increasing the resistance of a NiCrBSi coating to heat wear by means of combined laser heat treatment

Testing of NiCrBSi coatings formed by gas-powder laser cladding and combined laser heat treatment, including laser cladding and high-temperature annealing, were conducted under conditions of sliding friction on the Kh12M steel according to the pin-on-disk scheme. The combined processing resulting in the formation of large carbides and chromium borides in the coatings is shown to increase their wear resistance by a factor of 1.8 at sliding velocities of 6.1 and 9.3 m/s, when there is significant frictional heating of the friction surfaces. © 2018 Author(s)

The summertime 12-h wind oscillation with zonal wavenumber <i>s</i> = 1 in the lower thermosphere over the South Pole

International audienceMeteor radar measurements of winds near 95 km in four azimuth directions from the geographic South Pole are analyzed to reveal characteristics of the 12-h oscillation with zonal wavenumber one (s=1). The wind measurements are confined to the periods from 19 January 1995 through 26 January 1996 and from 21 November 1996 through 27 January 1997. The 12-h s=1 oscillation is found to be a predominantly summertime phenomenon, and is replaced in winter by a spectrum of oscillations with periods between 6 and 11.5 h. Both summers are characterized by minimum amplitudes (5?10 ms?1) during early January and maxima (15?20 ms?1) in November and late January. For 10-day means of the 12-h oscillation, smooth evolutions of phase of order 4?6 h occur during the course of the summer. In addition, there is considerable day-to-day variability (±5?10 ms?1 in amplitude) with distinct periods (i.e., ~5 days and ~8 days) which suggests modulation by planetary-scale disturbances. A comparison of climatological data from Scott Base, Molodezhnaya, and Mawson stations suggests that the 12-h oscillation near 78°S is s=1, but that at 68°S there is probably a mixture between s=1 and other zonal wavenumber oscillations (most probably s=2). The mechanism responsible for the existence of the 12-h s=1 oscillation has not yet been identified. Possible origins discussed herein include in situ excitation, nonlinear interaction between the migrating semidiurnal tide and a stationary s=1 feature, and thermal excitation in the troposphere

Nanostructuring and surface hardening of structural steels by ultrasonic impact-frictional treatment

With two structural steels (the steels 50 and 09G2S) as examples, the paper studies the effectiveness of a new method of ultrasonic impact-frictional treatment (UIFT) for the hardening and nanostructuring of the surface layer with the variation of the tilt angle of the vibrating indenter and the treatment environment. It is demonstrated that treatment with tool tilt angles different from 90° and with the absence of a contact liquid results in the formation of a nanostructured surface layer with increased microhardness. © 2018 Author(s)

Does the Babcock--Leighton Mechanism Operate on the Sun?

The contribution of the Babcock-Leighton mechanism to the generation of the Sun's poloidal magnetic field is estimated from sunspot data for three solar cycles. Comparison of the derived quantities with the A-index of the large-scale magnetic field suggests a positive answer to the question posed in the title of this paper.Comment: 5 pages, 2 figures, to apper in Astronomy Letter