Rolling friction of a viscous sphere on a hard plane

A first-principle continuum-mechanics expression for the rolling friction coefficient is obtained for the rolling motion of a viscoelastic sphere on a hard plane. It relates the friction coefficient to the viscous and elastic constants of the sphere material. The relation obtained refers to the case when the deformation of the sphere $\xi$ is small, the velocity of the sphere $V$ is much less than the speed of sound in the material and when the characteristic time $\xi/V$ is much larger than the dissipative relaxation times of the viscoelastic material. To our knowledge this is the first ``first-principle'' expression of the rolling friction coefficient which does not contain empirical parameters.Comment: 6 pages, 2 figure

Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding

[EN] The development of hardfacing coatings has become technologically significant in many industries A common approach is the production of metal matrix composites (MMC) layers. In this work NiCr-WC MMC hardfacing layers are deposited on C25 steel by means of laser cladding. Spheroidal fused tungsten carbides is used as reinforcement phase. Three different NiCr alloys with different Cr content were tested. Optimum conditions to obtain dense, uniform carbide distribution and hardness close to nominal values were defined. The effect of Cr content respect to the microstructure, susceptibility for cracking and the wear rate of the resulting coating will also be discussed. © 2011 Published by Elsevier Ltd.This works has been done under the financial support of Xunta de Galicia, project reference 08DPI024CT, Programa de Diseno y Produccion Industrial.Amado Paz, JM.; Tobar Vidal, MJ.; Yañez Casal, AJ.; Amigó Borrás, V.; Candel Bou, JJ. (2011). Crack Free Tungsten Carbide Reinforced Ni(Cr) Layers obtained by Laser Cladding. Physics Procedia. 12(1):338-344. https://doi.org/10.1016/j.phpro.2011.03.043S33834412

In-situ formation characteristic, tribological characterization and anti-corrosion properties of quaternary composites films

Improvements of wear and corrosion properties are essential characteristic in engineering application. A study was made on the structure, electro-oxidation and properties of fabricated Z

Effect of functional composite coating developed via sulphate and chloride process parameter on the UNS G10150 steel for structural and wear mitigation in defence application

The major engineering challenge of materials in defence technologies is the vulnerability of based metals to structural and wears deformation in service. In this paper, structural formation, mechanical and thermal stability behavior of developed composite coating of Zn-30Al-7%Ti/Sn chloride bath and Zn- 30Al-7%Ti/Sn sulphate bath was investigated and compared to provide mitigation against failure. The thermal ageing property was done for 2 h at 600 �C via isothermal furnace. The structural, interfacial effect and stability behaviors of the co-deposited alloys were evaluated using scanning electron microscope equipped with energy dispersive spectrometer (SEM/EDS), atomic force microscope (AFM) and Xray diffractometer (XRD). The hardness and wear properties of the deposited coatings were examined with diamond base micro-hardness tester and reciprocating sliding tester respectively. The result shows that Zn-30Al-7%Ti/Sn sulphate co-deposition contributed to increase hardness and wear resistance than Zn-30Al-7%Ti/Sn chloride bath alloy. The stable crystal growth and significant performance of Zn-30Al- 7%Ti/Sn sulphate are link to the intermetallic phase hybrid of ZnAl, Zn4TiAl2, Zn3AlTi. Besides, it was observed that Zn-30Al-7%Ti/Sn sulphate has excellent thermomechanical stability at harsh temperature, due to the deposition of Sn/Ti on steel; leading to formation of super-hard interface. However, it was established that co-deposition of mild steel with Zn-30Al-7%Ti/Sn in sulphate bath significantly improved the structural and wear performance. It was shown that the hardness and wear of the developed composite Zn-30Al-7%Ti/Sn is increased by about 80% compared to as received sample and about 25% compared with Zn-30Al-7%Ti/Sn chloride coating developed. The improvement was proved to be an interference of zinc-composite growth. Thus, this work shows that sulphate induced Zn-30Al-7%Ti/ Sn via generation of controllable process parameter can provide significant improvements in thin filmcoating for wear mitigation and structural improvement in defence application