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

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.

Evaluation of Residual Stresses and Fatigue Life of Tungsten Carbide Thermal Spray Coated Aircraft Landing Gear Materials

1998 ◽  
Author(s):  
R.T.R. Mcgrann ◽  
J.R. Shadley ◽  
E.F. Rybicki ◽  
B.E. Bodger ◽  
W.A. Emery ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Tungsten Carbide ◽  
Thermal Spray ◽  
Fatigue Tests ◽  
Landing Gear ◽  
Spray Coatings ◽  
Aircraft Landing ◽  
Aircraft Landing Gear ◽  
Flat Beam

Abstract Tungsten carbide thermal spray coatings have been used for more than twenty years in the commercial aircraft industry in applications such as turbine blade and flap-track wear surfaces. Additionally, the evaluation of tungsten carbide (WC) coatings to replace chrome plating in other aircraft applications has been underway for several years. For example, WC coatings applied by the high velocity, oxy-fuel (HVOF) process are being evaluated for use on aircraft landing gear parts. One factor that affects the suitability of WC coatings is the fatigue life of the coated part. This study compares the fatigue life of electrodeposited chrome plated specimens to the fatigue life of WC HVOF-sprayed specimens on aircraft landing gear alloys. Fatigue tests were run on cantilever flat beam specimens coated on one side and subjected to bending fatigue loads. Residual stress levels for the coatings were determined using the Modified Layer Removal Method on rectangular residual stress specimens processed with the flat beam specimens. Also, the Young's modulus and Poisson's ratio of the coating were determined using the Cantilever Beam Bending Method performed on beam specimens that were processed with the fatigue specimens and the residual stress specimens. Results indicate that certain levels of residual stress in the coating can enhance the fatigue life of the parts. The fatigue lives in bending tests of several WC coated specimens are compared with the fatigue life of chrome plated specimens.

Tungsten Carbide Coatings on the Fatigue Life in Bending of Thermal Spray Coated Aluminum The Effect of Residual Stress in HVOF

1998 ◽  
Vol 7 (4) ◽  
pp. 546-552 ◽  
Author(s):  
R.T.R. McGrann ◽  
D.J. Greving ◽  
J.R. Shadley ◽  
E.F. Rybicki ◽  
B.E. Bodger ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Tungsten Carbide ◽  
Thermal Spray ◽  
Carbide Coatings

Modeling Residual Stress Development in Thermal Spray Coatings: Current Status and Way Forward

2017 ◽  
Vol 26 (6) ◽  
pp. 1115-1145 ◽  
Author(s):  
Abba A. Abubakar ◽  
Abul Fazal M. Arif ◽  
Khaled S. Al-Athel ◽  
S. Sohail Akhtar ◽  
Javad Mostaghimi
Keyword(s):  
Residual Stress ◽  
Thermal Spray ◽  
Thermal Spray Coatings ◽  
Current Status ◽  
Stress Development ◽  
Spray Coatings

Variation in Residual Stress Field During Fatigue Failure of Thermal Spray Coatings

2000 ◽  
Author(s):  
R. Ahmed ◽  
M. Hadfield ◽  
S. Tobe
Keyword(s):  
Residual Stress ◽  
Thermal Spray ◽  
Fatigue Failure ◽  
Contact Stress ◽  
Rolling Direction ◽  
Rolling Contact ◽  
Thermal Spray Coatings ◽  
Residual Stress Field ◽  
Stress Measurements ◽  
Spray Coatings

Abstract A non-destructive experimental approach was adapted to investigate the variations in residual stress fields within thermal spray coatings. WC-Co coatings produced by a HVOF technique were considered for concentrated rolling sliding contacts in this study. These coatings were produced in various thicknesses on various substrates. Residual stress measurements were made using an x-ray diffraction technique, along and across the rolling direction. A modified four-ball machine was used to conduct rolling contact fatigue tests under various tribological conditions of contact stress, lubrication and contact configuration. Residual stress measurements were made before and after the tribological tests. Failed rolling elements were analyzed using scanning electron microscopy, electron probe microscopy and surface interferometry. Results indicate that the magnitude of compressive residual stress attenuates during fatigue failure. The magnitude of attenuated residual stress was dependent upon the type of tribological failure. This attenuation of residual stress was attributed to the microcracking of coating under the influence of contact stress.

Advanced thermal spray coatings for tribological applications

2007 ◽  
Vol 221 (3) ◽  
pp. 175-185 ◽  
Author(s):  
C Bartuli ◽  
T Valente ◽  
F Casadei ◽  
M Tului
Keyword(s):  
Thermal Spray ◽  
Spray Coating ◽  
Ceramic Coatings ◽  
Thermal Spray Coating ◽  
Thermal Spray Coatings ◽  
Solid Lubrication ◽  
Titanium Nitrides ◽  
Spray Coatings ◽  
Hybrid Techniques ◽  
Wear Protection

Thermal spray coating is one of the most common procedures to improve the tribological properties of materials. Ceramic and cermet coatings, especially those based on oxides (alumina, chromium oxide, etc.) and carbides, are widely used for wear protection. Improvements under investigations are related to the possible use of nanostructured coatings and to the potential application of hybrid techniques. As a possible alternative, solid lubrication is proposed as integration or replacement of the traditional liquid lubrication in the case of severe operative conditions when there is the possibility of a lack of lubricant or when environmental problems can arise from waste disposal. In the present paper, results from experimental activities on different types of abrasion-resistant thermal spray coatings are presented: graded coating systems, specifically designed for titanium-based alloys, obtained by reactive plasma spraying and physical vapour deposition of titanium nitrides; nanostructured WC-Co coatings deposited by high velocity oxy-fuel; plasma-sprayed ceramic coatings based on oxides containing nanophases either from nanostructured precursors or postprecipitated by purposely designed thermal treatments; self-lubricant coatings deposited by plasma spray with the inclusion of graphite.

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