An Overview of Using Small Punch Testing for Mechanical Characterization of MCrAlY Bond Coats

Chen, Hao; Jackson, George A.; Sun, Wei

doi:10.1007/s11666-017-0593-y

Cited by 25 publications

(9 citation statements)

References 105 publications

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“…Since the volume fraction of the β phase is around 30%, the CoNiCrAlY coating also exhibits a ductile-to-brittle transition behaviour. It has been reported from previous studies that the DBTT of this CoNiCrAlY coating is between 500-700 °C [26,35]. Thus to minimise the tendency of coating cracking during clamping at room temperature, it is proposed here that clamping at temperatures above DBTT can be an option to avoid the initial cracking.…”

Section: Discussionmentioning

confidence: 98%

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Some considerations in using the small punch testing for thermally sprayed CoNiCrAlY coatings

Chen

Rushworth

Sun

et al. 2019

Surface and Coatings Technology

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Small punch testing exhibits great potential in mechanical characterisation of thin coatings.This testing method can be used to determine the mechanical performance of thermally sprayed coatings, especially to qualitatively characterise the effects of coating defects on the mechanical behaviour. In this work, some considerations in using the small punch testing for coatings are presented through a microstructure evolution analysis of a vacuum plasma sprayed CoNiCrAlY coating under small punch test. The CoNiCrAlY coating was characterised with a large number of un-melted particles as the coating defects. It is shown that the clamping in the small punch test rig can result in micro-cracking around the unmelted particles in the coating prior to testing. It is also found that the un-melted particles in the coating act as predominant cracking sites and fast failure occurred around the un-melted particles. Careful considerations need to be taken into account when using the small punch test for coatings to avoid any changes in the coating microstructure and plasticity during the clamping stage.

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Section: Discussionmentioning

confidence: 98%

“…More recently, the application of SPT has been expanded to other areas where the availability of materials is limited, such as coatings [26]. In general, coatings exhibit unique mechanical and chemical properties when comparing to the bulk materials.…”

Section: Introductionmentioning

confidence: 99%

Some considerations in using the small punch testing for thermally sprayed CoNiCrAlY coatings

Chen

Rushworth

Sun

et al. 2019

Surface and Coatings Technology

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“…These values have been specified (5.2). 5. In discussion section, there are a number of statements made, could you please make them cleaner, by adding the reference or it is speculative by the current authors.…”

Section: Matlab Code Should Be Referenced?mentioning

confidence: 99%

“…CoNiCrAlY alloys have been widely used as bond coats for TBC systems because of low cost, improved control of composition and the feasibility to tailor the coating's microstructures [3,4]. A number of previous studies have investigated CoNiCrAlY coatings but have typically focused on oxidation behaviour with little attention given to the mechanical properties of the coatings [5][6][7]. This, in part, is because conventional mechanical testing techniques, such as uniaxial tensile testing, are not suitable for evaluating the mechanical properties of thin CoNiCrAlY bond coats, which are typically around 200 µm thick in a TBC [1].…”

Section: Introductionmentioning

confidence: 99%

An experimental and numerical study of a CoNiCrAlY coating using miniature specimen testing techniques

Wei

Jackson

et al. 2019

International Journal of Mechanical Sciences

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Small punch tensile (SPT) tests have been carried out for a CoNiCrAlY coating at room temperature (RT), 500°C and 700°C. Highly re-producible results have been obtained for SPT at 700°C while the formation of early cracking at lower temperatures tends to compromise the repeatability of the tests. An alternative novel miniature specimen testing method has been developed and used for the miniature tensile tests of the CoNiCrAlY coating in the same temperature range. Good agreements have been achieved between the SPT and miniature tensile testing results regarding the ductile to brittle transition temperature (DBTT). Excellent repeatability has been achieved over the full range of the temperature for the miniature tensile tests. An inverse approach has been developed and used to extract the mechanical properties of the material from the miniature tensile tests, using a temperature-dependent Johnson-Cook model. Finite element (FE) modelling of the SPT tests, including damage evolution, has been carried out using the extracted material properties to give comparable predictions of the SPT testing results, such as the loaddisplacement curves and the approximate locations of the fracture failures. KeywordsCoNiCrAlY coating; miniature tensile test; small punch tensile test; high temperature properties; inverse method; ductile-to-brittle transition Manuscript category SOLID MECHANICS

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“…To meet the demands for high gas turbine efficiency, turbine inlet temperatures have reached or even exceeded the maximum service temperature of superalloys [1][2][3]. It is extremely difficult for superalloy components to maintain their mechanical and chemical stability in such harsh operating environments [4].…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature on the β-phase depletion in MCrAlYs: A modelling and experimental study towards designing new bond coat alloys

Chen

Rushworth

Hou

et al. 2019

Surface and Coatings Technology

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This paper investigates the effects of varied temperature conditions on the kinetics of β-phase depletion in MCrAlYs by DICTRA diffusion simulations and experimental observations. A commercially available MCrAlY composition and two modelled compositions were examined at temperature regimes of 1000 °C, 1100 °C and 1200 °C. A previously developed temperature-dependent oxidation model was used at the boundary to examine the β-phase depletion kinetics at different temperatures. The oxide growth kinetics and the corresponding Al flux were calculated based on the oxidation model. The MCrAlY phase equilibrium calculations were conducted in Thermo-Calc and the oxidation-diffusion simulations were carried out using the finite difference diffusion software, DICTRA. It was found that the MCrAlYs exhibit a predominantly dual-phase γ+β structure at 1000 °C and above. It was revealed that varying the temperature had a strong effect on the β-phase depletion in low Alcontent MCrAlYs from DICTRA simulations and available experimental measurements. In *Manuscript Click here to view linked References addition, it was demonstrated from the diffusion simulations that MCrAlYs with high Al content exhibit an enhanced lifetime in maintaining the two-phase structure with less β-phase depletion at high temperatures due to the high Al and β-phase content.

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An Overview of Using Small Punch Testing for Mechanical Characterization of MCrAlY Bond Coats

Cited by 25 publications

References 105 publications

Some considerations in using the small punch testing for thermally sprayed CoNiCrAlY coatings

Some considerations in using the small punch testing for thermally sprayed CoNiCrAlY coatings

An experimental and numerical study of a CoNiCrAlY coating using miniature specimen testing techniques

Effects of temperature on the β-phase depletion in MCrAlYs: A modelling and experimental study towards designing new bond coat alloys

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