The effect of laser treatment of WC-Co coatings on their failure under thermal cycling

Kasterov, Artur; Шугуров, А. Р.; Kazachenok, Marina; Панин, А. В.; Cheng, Chin‐Hsiang; Chang, I-Ling

doi:10.1063/1.4966376

Cited by 1 publication

(3 citation statements)

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“…It is apparent that all ℎ , dependencies show similar qualitative behaviour, i.e. an increase in compressive stress and subsequent formation of radial tensile stresses, as discussed in our previous reports [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In the data, one can identify (i) varying maximum magnitudes of individual ℎ , dependencies (occurring in both domains, tensile and compressive alike) as well as (ii) slightly different shapes of the dependencies ℎ , ( ).…”

Section: Iiib Single Laser Pulse Experimentssupporting

confidence: 82%

“…The cyclic thermo-mechanical fatigue of WC-Co composites has been studied both experimentally [6,7,8] as well as using simulation tools to quantify thermal metal machining tool loads [9,10]. In order to predict the degree of local damage induced by the interrupted tool-workpiece contact and wear, a variety of material parameters have to be taken into account, such as CTEs, thermal conductivities and elasto-plastic properties of the coating-substrate composite, all of which are dependent on temperature, crystallite size as well as geometry and the time-scale of the underlying process.…”

Section: Introductionmentioning

confidence: 99%

“…In order to predict the degree of local damage induced by the interrupted tool-workpiece contact and wear, a variety of material parameters have to be taken into account, such as CTEs, thermal conductivities and elasto-plastic properties of the coating-substrate composite, all of which are dependent on temperature, crystallite size as well as geometry and the time-scale of the underlying process. Most recent experimental studies were devoted primarily to the ex-situ analysis of thermo-mechanically loaded inserts from real cutting experiments [2] and WC-Co composites treated in laser thermal shock experiments [7,8,11]. The latter provide the opportunity to evaluate the influence of controllably induced thermo-mechanical damage, separated from occurring friction loads.…”

Section: Introductionmentioning

confidence: 99%

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20 Hz synchrotron X-ray diffraction analysis in laser-pulsed WC-Co hard metal reveals oscillatory stresses and reversible composite plastification

Gruber

Kiefer

Rössler

et al. 2019

International Journal of Refractory Metals and Hard Materials

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The lifetime of WC-Co inserts used in cutting processes, such as milling, is limited by millisecond temperature and mechanical pulses, which occur as a result of interrupted tool-workpiece contact, thermal fatigue and wear. In the current work, synchrotron X-ray diffraction (XRD) was used in conjunction with a pulsed laser heating setup to characterise the time-dependent development of stresses and microstructure in locally irradiated WC-Co inserts coated by chemical vapour deposition with 6.5 and 3.5 µm thick TiCN and α-Al2O3 films, respectively. Diffraction data from the WC-Co phase were used to evaluate the time and temperature-dependent evolution of in-plane stresses, thermal strains and integral breadths of WC diffraction peaks in experiments with a single and five successive laser shocks applied within 2.2 and 20 seconds, respectively, using a laser spot diameter of ~5.8 mm and an X-ray beam size of 1 × 1 mm 2. The laser heating induces the formation of compressive stresses in the inserts' substrates. Above a temperature of ~750°C, at the onset of WC-Co composite plastification, compressive stresses relax and then vanish in WC at the maximal applied temperature of ~1300°C, followed by the build-up of tensile stresses. The applied cyclic heating up and cooling down led to the repetitive formation of compressive and tensile stresses, with temperature dependencies oscillating with the number of applied laser pulses. The observed relatively high tensile stress level of ~1100 MPa in WC was a consequence of the stabilising function of the coating, which hindered the initiation of surface hot cracks and stress relaxation. The stress evolution was coupled with changes in XRD peak broadening, which however strongly depended on the particular hkl reflections and showed oscillatory behaviour within a single temperature cycle. In summary, the unique diffraction setup revealed stress levels and provides insight into the WC-Co composite plastification mechanism governing the stress build-up and relaxation in locally thermo-shocked WC-Co inserts at millisecond time resolution.

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