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Title: Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters

Abstract

Thermal spray deposited WC-CoCr coatings are extensively used for surface protection of wear prone components in a variety of applications. Although the primary purpose of the coating is wear and corrosion protection, many of the coated components are structural systems (aero landing gear, hydraulic cylinders, drive shafts etc.) and as such experience cyclic loading during service and are potentially prone to fatigue failure. It is of interest to ensure that the coating and the application process does not deleteriously affect the fatigue strength of the parent structural metal. It has long been appreciated that the relative fatigue life of a thermal sprayed component can be affected by the residual stresses arising from coating deposition. The magnitude of these stresses can be managed by torch processing parameters and can also be influenced by deposition effects, particularly the deposition temperature. In this study, the effect of both torch operating parameters (particle states) and deposition conditions (notably substrate temperature) were investigated through rotating bending fatigue studies. The results indicate a strong influence of process parameters on relative fatigue life, including credit or debit to the substrate's fatigue life measured via rotating bend beam studies. Damage progression within the substrate was further explored bymore » stripping the coating off part way through fatigue testing, revealing a delay in the onset of substrate damage with more fatigue resistant coatings but no benefit with coatings with inadequate properties. Finally, the results indicate that compressive residual stress and adequate load bearing capability of the coating (both controlled by torch and deposition parameters) delay onset of substrate damage, enabling fatigue credit of the coated component.« less

Authors:
 [1];  [1]
  1. Stony Brook Univ., NY (United States). Center for Thermal Spray Research
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
Stony Brook Univ., NY (United States); USDOE
OSTI Identifier:
1345538
Alternate Identifier(s):
OSTI ID: 1361652
Report Number(s):
SAND-2017-0715J; SAND-2016-9625J
Journal ID: ISSN 0257-8972; PII: S0257897217302165
Grant/Contract Number:
AC04-94AL85000
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Surface and Coatings Technology
Additional Journal Information:
Journal Volume: 315; Journal Issue: C; Journal ID: ISSN 0257-8972
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; thermal spray; high velocity oxy-fuel; fatigue; residual stress; WC-CoCr

Citation Formats

Vackel, Andrew, and Sampath, Sanjay. Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters. United States: N. p., 2017. Web. doi:10.1016/j.surfcoat.2017.02.062.
Vackel, Andrew, & Sampath, Sanjay. Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters. United States. doi:10.1016/j.surfcoat.2017.02.062.
Vackel, Andrew, and Sampath, Sanjay. Mon . "Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters". United States. doi:10.1016/j.surfcoat.2017.02.062. https://www.osti.gov/servlets/purl/1345538.
@article{osti_1345538,
title = {Fatigue behavior of thermal sprayed WC-CoCr- steel systems: Role of process and deposition parameters},
author = {Vackel, Andrew and Sampath, Sanjay},
abstractNote = {Thermal spray deposited WC-CoCr coatings are extensively used for surface protection of wear prone components in a variety of applications. Although the primary purpose of the coating is wear and corrosion protection, many of the coated components are structural systems (aero landing gear, hydraulic cylinders, drive shafts etc.) and as such experience cyclic loading during service and are potentially prone to fatigue failure. It is of interest to ensure that the coating and the application process does not deleteriously affect the fatigue strength of the parent structural metal. It has long been appreciated that the relative fatigue life of a thermal sprayed component can be affected by the residual stresses arising from coating deposition. The magnitude of these stresses can be managed by torch processing parameters and can also be influenced by deposition effects, particularly the deposition temperature. In this study, the effect of both torch operating parameters (particle states) and deposition conditions (notably substrate temperature) were investigated through rotating bending fatigue studies. The results indicate a strong influence of process parameters on relative fatigue life, including credit or debit to the substrate's fatigue life measured via rotating bend beam studies. Damage progression within the substrate was further explored by stripping the coating off part way through fatigue testing, revealing a delay in the onset of substrate damage with more fatigue resistant coatings but no benefit with coatings with inadequate properties. Finally, the results indicate that compressive residual stress and adequate load bearing capability of the coating (both controlled by torch and deposition parameters) delay onset of substrate damage, enabling fatigue credit of the coated component.},
doi = {10.1016/j.surfcoat.2017.02.062},
journal = {Surface and Coatings Technology},
number = C,
volume = 315,
place = {United States},
year = {Mon Feb 27 00:00:00 EST 2017},
month = {Mon Feb 27 00:00:00 EST 2017}
}

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  • Thermal spray deposited WC-CoCr coatings are extensively used for surface protection of wear prone components in a variety of applications. Although the primary purpose of the coating is wear and corrosion protection, many of the coated components are structural systems (aero landing gear, hydraulic cylinders, drive shafts etc.) and as such experience cyclic loading during service and are potentially prone to fatigue failure. It is of interest to ensure that the coating and the application process does not deleteriously affect the fatigue strength of the parent structural metal. It has long been appreciated that the relative fatigue life of amore » thermal sprayed component can be affected by the residual stresses arising from coating deposition. The magnitude of these stresses can be managed by torch processing parameters and can also be influenced by deposition effects, particularly the deposition temperature. In this study, the effect of both torch operating parameters (particle states) and deposition conditions (notably substrate temperature) were investigated through rotating bending fatigue studies. The results indicate a strong influence of process parameters on relative fatigue life, including credit or debit to the substrate's fatigue life measured via rotating bend beam studies. Damage progression within the substrate was further explored by stripping the coating off part way through fatigue testing, revealing a delay in the onset of substrate damage with more fatigue resistant coatings but no benefit with coatings with inadequate properties. Finally, the results indicate that compressive residual stress and adequate load bearing capability of the coating (both controlled by torch and deposition parameters) delay onset of substrate damage, enabling fatigue credit of the coated component.« less
  • The WC-Co powders can be used to produce good adhesive and wear resistant HVOF thermal spray coatings on steel and light alloys substrates. In order to understand the properties of this kind of coating, the phases which are present in the coatings and structure changes during post heat treatments have been investigated. Although the coating properties depend very much on the structure developed in the substrate-coating interfacial region it has not been yet investigated in detail. The present study is devoted to the experimental and theoretical analysis of this interfacial region. The structure characterization has been performed mainly through themore » use of transmission electron microscopy. To provide a theoretical investigation a realistic prediction model of the process has been developed and on its base the mathematical simulation of the substrate-coating thermal interaction has been undertaken.« less
  • The microstructure and microhardness of high velocity oxygen fuel-sprayed WC-CoCr coatings were comparatively studied both before and after laser heat treatment of the coatings. Optical microscopy, scanning electron microscopy, X-ray diffraction and microhardness testing were applied to investigate the microstructure, phase composition, porosity and microhardness. The results indicate that WC is still present, and W{sub 2}C has appeared, while neither cobalt nor {sigma}-CrCo is detectable. Co{sub 4}W{sub 2}C has appeared in the high velocity oxygen fuel-sprayed coating after laser heat treatment as compared to the coating before laser treatment. The relative content of the W{sub 2}C has not increased withmore » laser treatment, but the laser treatment has essentially eliminated the porosity almost entirely, providing a more homogeneous and densified microstructure. The laser heat treatment has effected the formation of a denser compact coating on the substrate. After laser heat treatment, the thickness of the coating has decreased from 300 {mu}m to 225 {mu}m. This corresponds to an average porosity in the high velocity oxygen fuel-sprayed coating that is approximately five times greater than that in the subsequently laser heat-treated coating. The laser treatment has also resulted in an increased hardness of the coating near the surface, where the average value increased from Hv{sub 0.2} = 1262.4 in the coating before laser heat treatment to Hv{sub 0.2} = 1818.7 after laser heat treatment.« less
  • HVOF thermally sprayed WC/Co coatings are applied onto components which are exposed to wear caused by abrasion, erosion, fretting and sliding. Beside wear attacks and static stresses in lots of cases alternating mechanical stresses caused by dynamic loads occur additionally. Therefore, the fatigue resistance of WC/Co 88/12 and WC/Co 83/17 coated specimens was investigated by high-cycle fatigue tests (HCF). The results of the fatigue tests were documented in statistically ascertained Woehler-diagrams (S-N-curves). Furthermore, the mechanisms of failure are discussed.
  • The thermal-mechanical fatigue (TMF) behavior of IN-100, a cast nickel-base superalloy, has been investigated with a mechanical strain-temperature loop from 600{degrees}C to 1050{degrees}C (873 to 1323 K). Peak strains were applied at intermediate temperatures, giving simulation of real component parts. Tests with or without a mean strain were used. Other tests involved a longer period or a tensile hold time, and they were compared with conventional in-phase TMF cycles. An interrupted test procedure was used to define a conventional TMF life to 0.3-mm crack depth, as well as a life to 50-{mu}m, crack depth, to characterize the crack initiation period.more » Some stress-strain hysteresis loops were reported. Thermal-mechanical fatigue life was dependent upon test parameters, while the life to crack initiation was not. Oxidation and microcracks were important in all the tests. These results were compared with those under low cycle fatigue at high temperature.« less