Original paper(Vol.47 No.4 pp.413)

Evaluation of delamination strength of thermally sprayed coating by edge-indentation method

Nakasa Keijiro; Kato Masahiko; Zhang Dongkun; Tasaka Keiichiro

Abstract:In order to evaluate the shear-deformation strength of thermally sprayed coatings, an 'edge-indentation method' was newly proposed in the present study, and the method was applied to WC-Co coating deposited on a tool (JIS:SKD5) steel specimen by high-velocity flame spraying and Al2O3-TiO2 coating on a mild steel (JIS:SS400) specimen by plasma spraying. The delamination energy of the WC-Co coating, Ed is defined by the following equation based on the indentation load P vs. displacement d curve: (equation is omitted)
The delamination energy Ed of WC-Co coating obtained by experiment reveals almost the same value irrespective of coating thickness B1 and relative indentation distance from edge x/B1. The Ed of Al2O3-TiO2 coating not only increases slightly with an increase in B1, and the Ed is smaller than that of WC-Co coating. The edge-indentation method is effective to evaluate the shear-delamination strength particularly when the substrates is very hard.

Key Words:delamination strength, thermal spray coating, edge-indentation method, load displacement curve, delamination area