Structural,Micromechanical and Tribological Characterization of Zn–Ni Coatings: Effect of Sulfate Bath Composition

Zn and Zn–Ni alloy coatings were electrodeposited on mild steel from sulfate-based bath containing Sn as additive. The effect of Ni content on the microstructure, morphology, microhardness and the tribological behavior of these coatings were studied and discussed. Adding Sn in the sulfate bath had a significant effect on the surface morphology, particularly on the Zn–8 wt% Ni coatings. By increasing the Ni concentration from 8 to 14 wt%, the X-ray patterns showed that the phase structure of Zn–Ni alloy coatings was changed from η-phase Ni₃Zn₂₂ to γ-phase Ni₅Zn₂₁. The plastic deformation and delamination were found to be wear mechanisms for the investigated coatings. While the Zn–14 wt% Ni alloys had the best wear resistance, Zn films had the most severe wear volume loss and the highest friction coefficient.     

Experimental Investigation of the Interface Behavior of Balanced and Unbalanced E-Glass/Polyester Woven Fabric Composite Laminates

The aim of this work is to study the influence of weave structure on the crack growth behavior of thick E-glass/polyester woven fabric composites laminates. Two different types of laminates were fabricated: (i) balanced: plain weave (taffetas T)/chopped strand mat weave (M) [T/M]₆ and (ii) unbalanced: 4-hardness satin weave (S)/chopped strand mat weave [S/M]₇. In order to accurately predict damage criticality in such structures, mixed mode fracture toughness data is required. So, the experiments were conducted using standards delamination tests under mixed mode loading and pure mode loading. These tests were carried out in mode II using End Load Split (ELS) tests and in mixed-mode I+II by Mixed Mode Flexure (MMF) tests under static conditions. The test methodology used for the experiments will be presented. The experimental results have been expressed in terms of total strain energy release rate and R-curves. The fracture toughness results show that the T/M interface is more resistant to delamination than the S/M interface.     

Crystal structure,thermal behaviour,vibrational spectroscopy and optical properties of new compounds K$$_{}$$Ca(HAsO$$_{4}$$4)$$_{}\cdot $$·H$$_{}$$O with kröhnkite-type chain

The new kröhnkite compound called potassium calcium-bis-hydrogen arsenate dihydrate K\(_{2}\)Ca(HAsO\(_{4})_{2}\cdot \)2H\(_{2}\)O was obtained by hydrothermal method and characterized by X-ray diffraction, infrared spectroscopy, Raman scattering, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis and optical (photoluminescence and absorption) properties. It crystallizes in the triclinic space group P\(\bar{1}\) and unit cell parameters \(a = 5.971(3)\) Å, \(b =6.634(3)\) Å, \(c = 7.856(4)\) Å, \(\alpha =104.532(9)\) \(^{\circ }\), \(\beta = 105.464(9)\) \(^{\circ }\) and \(\gamma = 109.698(9)\) \(^{\circ }\). The structure of K\(_{2}\)Ca(HAsO\(_{4})_{2}\cdot \)2H\(_{2}\)O built up from this infinite, (Ca(HAsO\(_{4})_{2}\)(H\(_{2}\)O)\(_{2})^{2+}\), was oriented along an axis resulting from the association of CaO\(_{6}\) octahedra alternating with each two HAsO\(_{4}\) tetrahedra by sharing corners. Each potassium atom links two adjacent chains by three oxygen atoms of HAsO\(_{4}\) tetrahedra. TGA and DSC have shown the absence of phase transition. The existence of vibrational modes corresponding to the kröhnkite is identified by the IR and Raman spectroscopies in the frequency ranges of 400–4000 and 20–4000 cm\(^{-1}\), respectively. The photoluminescence measurement show one peak at 507 nm, which is attributed to band–band (free electron–hole transitions) and (bound electron–hole transitions) emissions within the AsO\(_{4}\) inorganic part.     

Development and tribological characterisation of nanostructured Zn-Ni and Zn-Co coatings: a comparative study

Zn-Ni and Zn-Co alloy coatings were electrodeposited on mild steel from sulphate-based baths. The morphology, microstructure, microhardness and tribological behaviours of the coatings have been studied and discussed. While the Zn-5wt-% Co layers presented a nanocrystalline simple nodular structure (45?±?5?nm), the Zn-14wt-% Ni showed a particular structure called cauliflower morphology (30?±?7?nm). The X-ray diffraction analysis showed that each of the electrodeposits was formed from zinc solid solution with a uniform zinc-cobalt intermetallic phase γ₂ (CoZn₁₃) for Zn-5wt-% Co alloy. However, a single γ-phase (intermetallic compound Ni₅Zn₂₁) was presented for the Zn-14wt-% Ni alloys. The Zn-14wt-% Ni films were found to be harder and rougher than the Zn-5wt-% Co layers. Plastic deformation and oxide layers production were the main wear mechanisms for the investigated coatings. The Zn-14wt-% Ni coatings were found to have the best wear resistance due to their microhardness and particular structure.     

A comparative investigation of the tribological behavior and scratch response of polyester powder coatings filled with different solid lubricants

Employing coatings is one of the most effective methods to reduce friction and protect contacting surfaces from wear. The deposition of protective coatings from thermosetting polymer powders has witnessed a rapid growth as an ecological, economic and energy efficient technology. During the last few decades, many new deposition techniques have been developed, and more and more tribological coatings have been made available. In this context, our present investigation tried, firstly to analyze the friction and wear behavior of electrostatically sprayed polyester powder coatings deposited on an aluminum substrate and secondly to focus on the response of these thermosetting coatings to micromechanical deformation under scratch test loading. The effect of graphite and hexagonal boron nitride (hBN) solid lubricant fillers on the friction and wear behavior of polyester composite coatings was evaluated using a reciprocating tribometer under dry friction condition. The experimental findings show that the additions of graphite or hBN are effective in enhancing the wear life of polyester powder coatings. Meanwhile, under the same sliding conditions, the wear results revealed that the polyester coating filled with only 10 wt.% of graphite has a higher anti-wear ability compared to the polyester coating filled with the same weight fraction of hBN. Thus, the two reinforcing polyester matrix fillers play an important role in reducing the plastic deformation of the coatings and enhance the formation of thick third body between the sliding parts as the fraction of solid lubricant increases from 0 wt.% to 10 wt.%. From the scratch analyses, we deduced that coatings scratch behavior is severely affected by the kind and amount of fillers inside the polyester matrix. In fact, the best friction characteristic and scratch resistance are observed in the case of polyester coatings filled with very low amount of hBN (5 wt.%).     

Geometrically nonlinear analysis of FGM shells using solid-shell element with parabolic shear strain distribution

International Journal of Mechanics and Materials in Design - This paper presents a modified first-order enhanced solid-shell element formulation with an imposed parabolic shear strain distribution...