Evaluation of the residual stresses in 95wt%Al2O3-5wt% SiC wear protection coating using X-Ray diffraction technique

• Published in: IOP conference series. Materials Science and Engineering 2018-02, Vol.311 (1), p.12016
• Main Authors: Mahmoud, Adel K., Hammoudi, Zaid S., Rasheed, Samah
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Axial stress; Coatings; Compressive properties; Elastic properties; Flame spraying; Low carbon steels; Mathematical analysis; Modulus of elasticity; Poisson's ratio; Residual stress; Silicon carbide; Straight lines; Stress concentration; Stress distribution; Stress measurement; Substrates; Wear; X-ray diffraction
• ISSN: 1757-8981; 1757-899X
• DOI: 10.1088/1757-899X/311/1/012016

This paper aims to measuring the residual stresses practically in wear protection coatings using the sin2ψ method according to X-ray diffraction technique. The wear protection coatings used in this study was composite coating 95wt% Al2O3-5wt% SiC, while bond coat was AlNi alloy produced by using flame spraying technique on the mild steel substrate. The diffraction angle, 2θ, is measured experimentally and then the lattice spacing is calculated from the diffraction angle, and the known X-ray wavelength using Bragg's Law. Once the dspacing values are known, they can be plotted versus sin2ψ, (ψ is the tilt angle). In this paper, stress measurement of the samples that exhibit a linear behavior as in the case of a homogenous isotropic sample in a biaxial stress state is included. The plot of dspacing versus sin2ψ is a straight line which slope is proportional to stress. On the other hand, the second set of samples showed oscillatory dspacing versus sin2ψ behaviour. The oscillatory behaviour indicates the presence of inhomogeneous stress distribution. In this case the X-ray elastic constants must be used instead of Young's modulus (E) and Poisson ratio (ν)values. These constants can be obtained from the literature for a given material and reflection combination. The value of the residual stresses for the present coating calculated was compressive stresses (-325.6758MPa).