Surface Analysis of Shear Strength Tested Tungsten Carbide Thermal Spray Coatings+

Thermal spray processing has become an important powder-consolidation technique to yield new materials for extremes of temperature, radiation, wear, corrosion and mechanical stresses. High Velocity Oxy-Fuel (HVOF) spray coating process gives higher deposition densities and coating hardness; lower oxide content and porosity. The adhesive strength of thermal spray coatings is greatly effected by the interfacial impurities. The ring shear test method shown in Fig. 1 appears to give the most accurate results on shear adhesive strength. A typical ring shear test result of 88WC12Co 1/4" ring HVOF thermal spray coating on 4140 steel rod using a Jet kote thermal spray gun is shown in Fig. 2. Repeated ring shear tests on similar samples prepared under same spray and test conditions resulted in different shear bond strength and coating ring displacement before break off. We examined the ring shear tested coatings using a Zeiss DMS942 Scanning Electron Microscope (SEM) and Kevex Energy Dispersive X-ray Spectrometer (EDXS) with LPX1 Quantum Si(Li) Detector.

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Impurity Effects on Shear Adhesive Strength of Tungsten Carbide Thermal Spray Coatings on Steel

Microscopy and Microanalysis ◽

10.1017/s1431927600027719 ◽

2001 ◽

Vol 7 (S2) ◽

pp. 328-329

Author(s):

Seetala V. Naidu ◽

James D. Garber ◽

Gary A. Glassc

Keyword(s):

Surface Roughness ◽

Tungsten Carbide ◽

Thermal Spray ◽

Adhesive Strength ◽

Steel Substrate ◽

Spray Coating ◽

Thermal Spray Coating ◽

Test Method ◽

Coating Process ◽

Ring Shear

We have used High Velocity Oxy-Fuel (HVOF) thermal spray coating process to obtain tungsten carbide coatings on steel. It is important to control the powder quality and surface roughness of the substrate in the thermal spray coating process to obtain good adherence. The adhesive strength is greatly effected by the interfacial impurities. Most commonly used in the thermal spray industry is Al2O3 grit abrasive for good surface roughness of steel substrate to produce anchor patterns for the coating. The previous studies indicated that some fine Al2O3 particles are trapped in the rough surface grooves during this process. The ring shear test method, described previously, appears to give the most accurate results on shear adhesive strength. The ring shear strength test was comprised of a 0.02” thick and 0.25” wide ring coating on a 1” diameter cylindrical substrate rod. This rod is placed in a disk with a cylindrical hole of the rod size and an incremental pressure is applied on the rod.

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Investigation into the Effects of High Temperature on Mechanical Properties of Thermal Spray Coatings Applied by Plasma Spraying

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.284.1151 ◽

2018 ◽

Vol 284 ◽

pp. 1151-1156

Author(s):

Lenar N. Shafigullin ◽

A.R. Ibragimov ◽

A.I. Saifutdinov

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

High Temperature ◽

Thermal Spray ◽

Spray Coating ◽

Thermal Spray Coating ◽

Thermal Spray Coatings ◽

Spray Coatings ◽

Heat Treatment Of Coatings ◽

Double Heat Treatment

C. C. Berndt advanced investigations of mechanical properties of thermal spray coatings under 4-point bending. He found that this investigation method is sensitive to the mechanical properties of thermal spray coatings.This paper contains the detailed investigation results for thermal spray coatings of zirconium dioxide under 4-point bending, i.e. tests of the specimens subjected to spraying at varying conditions and pre-test soaking with the various duration at 1100 °С.It was established how the mechanical properties of thermal spray coatings changed depending on the spraying mode and high temperature soaking. The test results show that the double heat treatment of coatings is more preferable than one-time heat treatment as it make the properties change linearly. It is more easily controllable during operation of the components with thermal spray coating.

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