Adhesion tests for thermal spray coatings: Correlation of bond strength and interfacial toughness

Abstract

In this paper, experiments for determining the adhesion properties have been performed using two test methods; tensile adhesive test which is widely used in industry and interfacial indentation test still under development in research laboratories. Therefore, only few experimental data on the accuracy of the methods and on the potential in an industrial context are available. For that reason, dissimilar coating-substrate combinations covering different ranges of type of thermal spray coating-substrate systems were tested. Ceramic (Al 2 O 3 ) and metallic (80Ni-20Cr) coatings were deposited by flame spraying system with two different thicknesses on titanium alloy and steel substrates exhibiting each two distinct roughness levels. The distinguished coating properties include the interfacial toughness and adhesive strength. The impacts of interfacial roughness and the thickness of the coating on the adhesion were conducted, and some adhesion tendency was also observed. Typical bond strength values measured were from 40 up to 100 MPa, and the interfacial toughness obtained from 1 to 4 MPa m 0?5 . The correlation of tensile adhesive strength and interfacial toughness has been discussed.

Quantitative Topographical Characterization of Thermally Sprayed Coatings by Optical Microscopy

“…For scanning profilometers a typical data set has lateral step size of the data points between 1 and 100 lm. The typical total number of data points is about 10 5 . SM images and data sets contain several 10 6 data points.…”

“…An important issue for the successful application of such coatings is the control of the roughness of the substrate as well as of the coating. For good adhesion between the sprayed coating and the substrate, an optimal substrate surface topography is often needed (Ref 4,5). For medical implants the surface morphology and roughness on different length scales must be optimized for good adhesion of cells (Ref 6).…”

Influence of isothermal and cyclic heat treatments on the adhesion of plasma sprayed thermal barrier coatings

“…Previous tensile adhesion tests of APS and high-velocity oxyfuel sprayed TBC systems have shown that TBC systems mainly fracture close to the BC/TC interface and give adhesion strengths of 10-50 MPa, [34][35][36][37]. Fracture toughness measurement by Vickers indentation has also been shown applicable to coatings, [27,36,38,39], and a correlation has been found between tensile adhesion strength and interface indentation toughness, [27,36]. Tensile adhesion of heat treated coatings has been somewhat studied, [31,34,39,40]: TBC systems exposed to short, (2 h), heat treatments exhibited an increase in adhesion strength, [34], while thermal cycling decreased the adhesion strength, [40].…”

“…Several methods are available for evaluating the adhesion of TBCs, [27][28][29][30][31][32][33]. One of them, and the one of concern in the present study, is the tensile adhesion test (TAT) described in ASTM C633, according to which one uses a common tensile test machine to measure the adhesive strength of a TBC system.…”

Effect of Surface Roughness on Improved Lubricity under an Ironing Condition Using a Synthetic Mica-Organic Intercalation Compound

“…This effect is called an "anchoring effect", which is particularly well known in the field of anti-corrosive coatings, heat resistant coatings, and designable coatings. The anchoring effect improves lubricant performance for properties such as corrosion resistance, adhesion strength, and long-term sustainability of various functional properties [4][5][6].…”