Thermal Spray of Cemented Carbide Coatings in Off-Angle Spraying: Correlations Between Process, Coating Features/Characteristics and Performance

CVD diamond coating was deposited on to 13%wt. Co -containing tungsten cemented carbide surfaces using a hot filament chemical vapor deposition (HFCVD) to improve wear properties and performance of WC -13% wt . Co . Prior to the deposition of the diamond films, a W - C gradient intermediate layer had been sputtered on WC -13% wt . Co . The surface and cross-section morphology, phase transformation, and grain size distribution of the samples were investigated by means of field emission scanning electron microscope (SEM), X-ray diffractometer (XRD), and atomic force microscope (AFM), respectively. The results show that W - C gradient intermediate layers can effectively reduce the diffusion of Co in cemented carbide substrates during diamond deposition process, resulting high nucleation density and ultra smooth nanocrystalline diamond films.

Download Full-text

Fatigue Life in Bending and Coatings Residual Stress in Tungsten Carbide Thermal Spray Coatings

Thermal Spray 1997: Proceedings from the United Thermal Spray Conference ◽

10.31399/asm.cp.itsc1997p0737 ◽

1997 ◽

Author(s):

R.T.R. McGrann ◽

J.R. Shadley ◽

E.F. Rybicki ◽

D.J. Graving ◽

B.E. Badger ◽

...

Keyword(s):

Residual Stress ◽

Fatigue Life ◽

Tungsten Carbide ◽

Thermal Spray ◽

Thermal Spray Coatings ◽

Chrome Plating ◽

Spray Coatings ◽

Wear Protection ◽

Carbide Coatings ◽

Flat Beam

Abstract Tungsten caibide (WC) thermal spray coatings are being used for wear protection on selected components of aircraft. Tungsten carbide coatings are being used on aircraft flap tracks and fan and compressor blade mid-span dampers. However, a larger use of tungsten carbide coatings is being considered for other commercial aircraft applications where it would be used as a replacement for chrome plating. For instance, WC coatings are currently being tested on aircraft landing gear parts. One factor that affects the suitability of WC coatings for these applications is the fatigue life of the coated part. Coatings, whether chrome plating or thermal spray coating, can reduce the fatigue life of the part compared to an uncoated part. This study compares the fatigue life of uncoated 6061 aluminum specimens to the fatigue life of WC thermal sprayed coated 6061 aluminum specimens. The relation between the residual stress level in the coating and the fatigue life of the specimens is also investigated. Fatigue tests were run on cantilever flat beam specimens that were coated on one side. Specimens were cycled in bending so that the coatings experienced tensile fatigue stresses. Residual stress levels for each type of coating were determined using the Modified Layer Removal Method on specimens processed along with the cantilever flat beam specimens. Test results show that the fatigue life of the WC coated specimens is directly related to the level of compressive residual stress in the coating.

Download Full-text