Significance of quenching stress in the cohesion and adhesion of thermally sprayed coatings

Katayama, Seiji; Fukushima, Takeshi; Kitahara, Shigeru

doi:10.1007/bf02647160

Cited by 60 publications

(21 citation statements)

References 10 publications

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“…During thermal spraying, each molten lamella lands on an already solidified lamella or substrate. This generates microstresses, which are of a tensile nature within the individual splats [19] and are also referred as quenching stresses. These microstresses are generated at the interface of the lamellas and at the coating substrate interface.…”

Section: Effect Of Residual Stressmentioning

confidence: 99%

Rolling contact fatigue of surface coatings—a review

Stewart¹,

Ahmed²

2002

Wear

132

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The aim of this review is to survey the state of the art relating to the rolling contact fatigue (RCF) investigation of various overlay coatings and also, to ascertain the influence of design parameters such as the type of deposition process, coating material and thickness on the RCF performance. Rolling contact fatigue is a significant factor in the failure of components in rolling/sliding contact. Although, sintered ceramics have provided improvements in RCF life of components in rolling/sliding contact, e.g. hybrid ceramic bearings, the economic and technological constraints associated have so far limited their use to specialist applications. Physical and chemical vapor deposition (PVD, CVD) as well as thermal spraying are methods of depositing overlay coatings. The designer must thus choose a deposition method based on economic and technical flexibility, e.g. material choice, functional grading, etc. Amongst this family of overlay coatings, PVD coatings are already finding commercial use whilst others are at a research and development stage. The available literature on the RCF testing of various types of overlay coatings is considerable, but it is generally difficult to synthesize all of the results to obtain a comprehensive understanding of the parameters which can have a significant effect on a coating's resistance to rolling contact fatigue. This review thus compares the RCF performance of these overlay coatings and discusses the results in terms of coating processes, materials, thickness, residual stress and tribological conditions of contact stress and lubrication.

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Section: Effect Of Residual Stressmentioning

confidence: 99%

Rolling contact fatigue of surface coatings—a review

Stewart¹,

Ahmed²

2002

Wear

132

View full text Add to dashboard Cite

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“…This indicated the stress was larger enough to drive any kind of cracking during splat deposition. Generally, the quenching stress was considered to be the cracking stress during cooling process [23][24][25]39]. As we know, the quenching stress results from the temperature difference at difference positions, which dictates:…”

Section: Origin Of the Cracking Stressmentioning

confidence: 99%

“…Unfortunately, the formation mechanism of the transverse pores remains unclear till today. It is widely accepted that vertical cracks result from the quenching stress during splat cooling [23][24][25]. While the transverse pores are considered to be retained (as residual voids) during the formation process of splats for some reasons and such phenomena as: low impact pressure [26,27], condensates and adsorbates on substrate surface [28,29].…”

Section: Introductionmentioning

confidence: 99%

Epitaxial growth and cracking of highly tough 7YSZ splats by thermal spray technology

Chen

Yang

2017

J Adv Ceram

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Thermally sprayed coatings are essentially layered materials and contain large numbers of lamellar pores. It is thus quite necessary to clarify the formation mechanism of lamellar pores which significantly influence coating performances. In the present study, to elaborate the formation mechanism of lamellar pores, the yttria-stabilized zirconia (ZrO 2 -7 wt% Y 2 O 3 , 7YSZ) splats, which have high fracture toughness and tetragonal phase stability, were employed. Interestingly, anomalous epitaxial growth occurred for all deposition temperatures in spite of the extremely high cooling rate, which clearly indicated chemical bonding and complete contact at splat/substrate interface before splat cooling. However, transverse spallation substantially occurred for all deposition temperatures in spite of the high fracture toughness of 7YSZ, which revealed that the lamellar pores were from transverse cracking/spallation due to the large stress during splat cooling. Additionally, fracture mechanics analysis was carried out, and it was found that the stress arose from the constraint effect of the shrinkage of the splat by locally heated substrate with the value about 1.97 GPa. This clearly demonstrated that the stress was indeed large enough to drive transverse cracking/spallation forming lamellar pores during splat cooling. All of these contribute to understanding the essential features of lamellar bonding and further tailoring the coating structures and performance.

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“…Various processing parameters are known to affect adhesion of sprayed coatings such as surface preparation of substrate, temperature of substrate during spraying, and residual stresses (Ref [3][4][5][6]. There are a number of testing methods to evaluate adhesion strength or interfacial fracture toughness of coatings such as pin test, shear adhesion test, bending test, peeling test and double cantilever beam (DCB) test, interfacial indentation test, and so on ( .…”

Section: Introductionmentioning

confidence: 99%

Tensile Test Specimens with a Circumferential Precrack for Evaluation of Interfacial Toughness of Thermal-Sprayed Coatings

et al. 2008

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A new testing procedure to evaluate the interfacial toughness of thermal-sprayed coatings has been developed. The newly designed test specimen is a modification of the pin test with an artificially introduced weak interface, which is expected to open up easily under tensile loading and act as a circumferential precrack along the interface between a coating and the substrate. This configuration makes it possible to calculate the stress intensity factor K Int at the tip of the precrack, which can be expressed aswhere r 0 is the apparent average stress, a the crack length, R the specimen radius, and F I the geometrical correction function. Finite-element analysis was carried out to calculate the correction function F I for various values of a/R. In the experiments, the flat surface of a pin was gritblasted and a ring-shaped area from the periphery was covered with carbon using a pencil and set into a mating dice. SUS316L stainless steel was plasma-sprayed onto the flat surface of the pin and the dice. Then, tensile load was applied to the pin to break the weak interface containing the carbon and finally the unmodified coating-substrate interface. The load required to pull out the pin was measured for various specimen parameters such as a and R. The results indicate that the adhesion of the tested coatings can be represented by interface toughness of 1.9 ± 0.1 MPa m 1/2 . As a consequence, this testing procedure can be considered as a viable method to evaluate adhesion of a thermal-sprayed coating on a substrate.

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Significance of quenching stress in the cohesion and adhesion of thermally sprayed coatings

Cited by 60 publications

References 10 publications

Rolling contact fatigue of surface coatings—a review

Rolling contact fatigue of surface coatings—a review

Epitaxial growth and cracking of highly tough 7YSZ splats by thermal spray technology

Tensile Test Specimens with a Circumferential Precrack for Evaluation of Interfacial Toughness of Thermal-Sprayed Coatings

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