Investigation on the mechanical performance of the electroless Ni–W–P coating based on fractal theory

Abstract

Engineering surface shows fractal characteristics, and mechanical performance of electroless Ni-W-P coating with fractal parameters can avoid the effects of instrument resolution and sampling length. In the present work, the ternary Ni-W-P coatings were deposited on mild steel (1015) polished with various sandpapers. Surface morphology of coating and mechanical property, including matrix roughness, adhesion strength, friction behavior and elastic modulus were investigated by using scanning electron microscopy (SEM) and MFT-4000 multifunctional material surface performance instrument, respectively. The results present that the mechanical property of the electroless Ni-W-P coating is affected by the fractal features. The stress in the direction of matrix surface is considered to decrease due to the rougher matrix. Meanwhile, the elements are prone to be deposited and the adhesion strength between Ni-W-P coating and matrix is seen to increase. The experiments also indicate that the friction coefficient of coating reduces as the fractal dimension of coating increase. However, the regularity of the relationship between fractal dimension and elastic modulus of Ni-W-P coating is inconspicuous while the elastic modulus is mainly affected by its own chemical component. The work provides evidence that the fractal dimension has a significant influence on the mechanical property of the electroless Ni-W-P coating. Nomenclature V deposition rate [mg mm −2 h −1 ]RECEIVED

Robustness of Surface Roughness against Low Number of Picture Elements and Its Benefit for Scaling Analysis

“…The specific process of flatten modification is as follows: The surface topography of a sub-image is extracted line by line into height sequences. Each height sequence is least-squares fitted by using a polynomial with an order of 1 or 2 (i.e., the flatten order), as shown in Equations ( 4) and (5), respectively. Then the polynomial was subtracted from the height sequence to provide the relative height sequence.…”

“…The analysis of surface features is of great significance and is widely applied in relevant fields, such as natural geographical topography [1], and in determining various surface morphology performance [2][3][4], and evaluating nanostructured-thin film property [5][6][7]. Zhang et al [8] and Hosseinabadi et al [9] reported a series of analyses on the rough surface of multiscale structures by calculating their fractal dimensions.…”

Study on Heat Transfer Performance and Anti-Fouling Mechanism of Ternary Ni-W-P Coating

“…The characterization of thermal physical parameters of micro-scale Ni-W-P coating will be further carried out in our subsequent research. Now, take the thermal conductivity of Ni-W-P coating into the equation We can obtain the thermal conductivity of Ni-W-P coating from Equation (8). Then, the change of it with the variety of ambient temperature, as well as differences of W element content at constant temperature can be analyzed.…”

“…where Φ 2 is the heat exchange amount of substrate with Ni-W-P coating, W. δ 2 is the thickness of Ni-W-P coating, m. λ 2 is the thermal conductivity of Ni-W-P coating, W/(m•K). T 3 is the cool side temperature of Ni-W-P coating, K. We can obtain the thermal conductivity of Ni-W-P coating from Equation (8). Then, the change of it with the variety of ambient temperature, as well as differences of W element content at constant temperature can be analyzed.…”

“…The fouling problem, which is regarded as "the main unresolved problem in heat transfer", is mainly generated by the deposition of particulates, impurities, salts, and various organic species onto heat transfer surfaces [1][2][3]. It can be seen from Figure 1 that the fouling of calcium carbonate Since the 1980s, electroless plating has been treated as an operational technology of the surface modification, attracting widespread attention [4][5][6][7][8]. The results prove that electroless Ni-P-based coating is an advantageous method for fouling inhibition [9][10][11][12][13].…”