Residual Stress in Oxide on NiCrAlY Coating Evaluated by Photoluminescence Spectroscope

2013 ◽  
Vol 750 ◽  
pp. 27-30 ◽  
Author(s):  
Hai Qiang Wang ◽  
Takeshi Osaki ◽  
Yukiko Nakahara ◽  
Shi Jie Zhu
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Residual Stresses ◽  
Exposure Time ◽  
Thermal Exposure ◽  
High Velocity Oxygen Fuel ◽  
Exposure Temperature ◽  
Thermal Grown Oxide ◽  
Nicraly Coating ◽  
Oxygen Fuel

The purpose of this study was to understand the effects of thermal exposure temperature on residual stress in thermal grown oxide (TGO) on NiCrAlY coating. The residual stresses in the TGO layer were measured by photo-stimulated luminescence spectrum. High velocity oxygen fuel sprayed (HVOF) method was used to fabricate NiCrAlY coating material. The thermal exposure tests were conducted in air at 900°C, 1000°C, 1100°C for up to 1000 hours using an electric furnace. It was shown that the thickness of the TGO increases with an increase in thermal exposure time with a parabolic curve. The residual stress in the TGO layer increases in thermal exposure time up to 75 hours, and then, the residual stress in the TGO layer decreases slowly. The effects of surface roughness on the residual stress in the TGO were discussed based on experimental results and analysis.

scholarly journals Effects of Roughness on Stresses in an Oxide Scale Formed on a Superalloy Substrate

Coatings ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 479
Author(s):  
Yang Zhao ◽  
Fan Sun ◽  
Peng Jiang ◽  
Yongle Sun
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Residual Stresses ◽  
Oxide Scale ◽  
Rough Surface ◽  
Alumina Scale ◽  
Growth Stress ◽  
Oxide Growth ◽  
Substrate Thickness ◽  
Roughness Effect

The effects of surface roughness on the stresses in an alumina scale formed on a Fecralloy substrate are investigated. Spherical indenters were used to create indents with different radii and depths to represent surface roughness and then the roughness effect was studied comprehensively. It was found that the residual stresses in the alumina scale formed around the rough surface are almost constant and they are dominated by the curvature rather than the depth of the roughness. Oxidation changes the surface roughness. The edge of the indent was sharpened after oxidation and the residual stress there was released presumably due to cracking. The residual stresses in the alumina scale decrease with increase in oxidation time, while the substrate thickness has little effect, given that the substrate is thicker than the alumina scale. Furthermore, the effect of roughness on the oxide growth stress is analysed. This work indicates that the surface roughness should be considered for evaluation of stresses in coatings.

scholarly journals Strategy of Residual Stress Determination on Selective Laser Melted Al Alloy Using XRD

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 451 ◽  
Author(s):  
Yujiong Chen ◽  
Hua Sun ◽  
Zechen Li ◽  
Yi Wu ◽  
Yakai Xiao ◽  
...  
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Residual Stresses ◽  
High Surface ◽  
Al Alloy ◽  
X Ray Diffraction ◽  
Scanning Strategy ◽  
Surface Distribution ◽  
Finished Surface ◽  
Microstructural Morphology

Selective laser melting (SLM) is known to generate large and anisotropic residual stresses in the samples. Accurate measurement of residual stresses on SLM-produced samples is essential for understanding the residual stress build-up mechanism during SLM, while a dramatic fluctuation can be observed in the residual stress values reported in the literature. On the basis of studying the influence of surface roughness on residual stress measured using X-ray diffraction (XRD), we propose a procedure coupling XRD technique with pretreatment consisting of mechanical polishing and chemical etching. The results highlight that residual stresses measured using XRD on as-built SLM-produced samples with high surface roughness are significantly lower than those measured on samples with finished surface, which is due to the stress relaxation on the spiked surface of as-built samples. Surface distribution of residual stresses and the effect of scanning strategy were systematically investigated for SLM-produced AlSi10Mg samples. Microstructural morphology was observed at the interface between sample and building platform and was linked to the surface distribution of residual stresses. This procedure can help us accurately measure the residual stresses in SLM-produced samples and thus better understand its build-up mechanism during the SLM process.

Effect of Surface Roughness and Residual Stress Induced by High Speed Milling Process on Short Crack Growth

2016 ◽  
Author(s):  
B. Zheng ◽  
H. D. Yu ◽  
X. Wang ◽  
X. M. Lai
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Residual Stresses ◽  
Crack Growth ◽  
Damage Evolution ◽  
High Speed ◽  
Milling Process ◽  
Short Crack ◽  
Machining Process ◽  
Effect Of Surface

Surface scratches and residual stresses inevitably appear on the surface of the component as a result of the machining process. The damage evolution of surface scratch due to the combined effect of cyclic loading and residual stresses will be significantly different from the case where only the cyclic loading is considered. In the damage evolution of surface scratch, the short crack growth is of great importance owing to its apparently anomalous behaviors compared with the long-crack growth. In this paper, the effect of the surface roughness and the residual stress on the short crack growth is studied. Firstly, the surface roughness and the residual stress of 7075-T6 aluminum alloy induced by the high speed milling process with various cutting speeds and feed rates are investigated with the experimental method. The maximum height roughness parameter is measured, which is regarded as the surface defect induced by the milling process. The residual stress on the specimen surface is measured with the X-ray diffraction. Results show that the surface roughness becomes higher with the increase of the feed rate. However, the influence of the cutting speed on the surface roughness is not significant. The residual stresses on the specimen surface are all in the compressive state. The residual stress is more compressive as the feed rate increases. The effects of the process parameters on the surface roughness and the residual stress are described by the fitted formulas. Then a modified model is built to characterize short fatigue crack growth behaviors with the consideration of the residual stress. This model is proved to provide a realistic treatment of the short crack growth, as reflected by comparison with experimental fatigue crack growth data of medium carbon steel and 7075-T6 aluminum alloy published in literature. The effect of surface roughness and residual stress caused by the milling process on the short crack growth is also investigated by using the proposed model. The growth of the scratch is nonlinear when it is subjected to the cyclic load. The compressive residual stress reduces the growth rate of the crack. The crack with larger initial surface roughness grows faster than that with smaller roughness. The correlation of surface roughness, residual stress and crack growth length is obtained by the polynomial fitting. The investigations in this paper can help the damage tolerance design of structures and improve the awareness of the effect of the residual stress and surface roughness induced by the machining process on the short crack growth.

scholarly journals Influence of Sandblasting Particle Size and Pressure on Resin Bonding Durability to Zirconia: A Residual Stress Study

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5629
Author(s):  
Sung-Min Kwon ◽  
Bong Ki Min ◽  
Young Kyung Kim ◽  
Tae-Yub Kwon
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Contact Angle ◽  
Particle Size ◽  
Residual Stresses ◽  
Zirconia Ceramic ◽  
Ceramic Surface ◽  
M Phase ◽  
Bonding Durability ◽  
Resin Bonding

The influence of residual stress induced by sandblasting the zirconia ceramic surface on the resin bonding to the ceramic is still unclear. The effect of four different sandblasting conditions (with 50 and 110 μm alumina at pressures of 0.2 and 0.4 MPa) on the bonding of adhesive resin cement (Panavia F 2.0) to zirconia (Cercon® ht) was investigated in terms of residual stress. The surface roughness and water contact angle of the zirconia surfaces were measured. The tetragonal-to-monoclinic (t–m) phase transformation and residual stresses (sin2ψ method) were studied by X-ray diffraction. The resin-bonded zirconia specimens were subjected to shear bond strength (SBS) tests before and after thermocycling (10,000 and 30,000 cycles) (n = 10). As the particle size and pressure increased, the roughness gradually and significantly increased (p = 0.023). However, there were no significant differences in roughness-corrected contact angle among all the sandblasted groups (p > 0.05). As the particle size and pressure increased, the m-phase/(t-phase + m-phase) ratios and compressive residual stresses gradually increased. After thermocycling, there were no significant differences in SBS among the sandblasted zirconia groups (p > 0.05). In conclusion, increased surface roughness and residual stress do not directly affect the resin bonding durability.

Characteristics of MCrAlY Coatings Sprayed by High Velocity Oxygen-Fuel Spraying System

1999 ◽  
Vol 122 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Y. Itoh ◽  
M. Saitoh ◽  
M. Tamura
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
High Velocity ◽  
Gas Turbines ◽  
High Velocity Oxygen Fuel ◽  
Hvof Spraying ◽  
Vacuum Plasma ◽  
Mcraly Coatings ◽  
Plasma Sprayed ◽  
Oxygen Fuel

High velocity oxygen-fuel (HVOF) spraying system in open air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Fe, Ni and/or Co) coatings can be applied to provide resistance against oxidation and corrosion to the hot parts of gas turbines. Also, it is well known that the thicker coatings can be sprayed in comparison with any other thermal spraying systems due to improved residual stresses. However, thermal and mechanical properties of HVOF coatings have not been clarified. Especially, the characteristics of residual stress, that are the most important property from the view point of production technique, have not been made clear. In this paper, the mechanical properties of HVOF sprayed MCrAlY coatings were measured in both the case of as-sprayed and heat-treated coatings in comparison with a vacuum plasma sprayed MCrAlY coatings. It was confirmed that the mechanical properties of HVOF sprayed MCrAlY coatings could be improved by a diffusion heat treatment to equate the vacuum plasma sprayed MCrAlY coatings. Also, the residual stress characteristics were analyzed using a deflection measurement technique and a X-ray technique. The residual stress of HVOF coating was reduced by the shot-peening effect comparable to that of a plasma spray system in open air. This phenomena could be explained by the reason that the HVOF sprayed MCrAlY coating was built up by poorly melted particles. [S0742-4795(00)00701-8]

A Study on Grinding Parameter Optimization of Reaction Bonded Silicon Carbide

2013 ◽  
Vol 631-632 ◽  
pp. 660-665 ◽  
Author(s):  
Yao Wang ◽  
Zha Yan Feng
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Silicon Carbide ◽  
Residual Stresses ◽  
Compressive Residual Stress ◽  
Bending Strength ◽  
Grinding Parameters ◽  
Depth Analysis ◽  
Cut Depth ◽  
Full Factorial

In order to enhance the efficiency and the surface smooth degree of the RBSiC grinding, a three factors two levels full factorial design was utilized to optimize the process. Combined with the effects of grinding parameters on surface roughness, the grit cut depth analysis was employed to choose the appropriate grinding parameters. The strength reliability and the residual stresses of the RBSiC ground using the optimized parameters were investigated. The results show that comparing to the polished RBSiC the ground ones have higher compressive residual stress, lower crack scatter and similar average bending strength.

Sign in / Sign up

Export Citation Format

Share Document