scholarly journals Thermally Assisted Machine Hammer Peening of Arc-Sprayed ZnAl-Based Corrosion Protective Coatings

2021 ◽  
Vol 5 (4) ◽  
pp. 109
Author(s):  
Andreas Wirtz ◽  
Mohamed Abdulgader ◽  
Michael P. Milz ◽  
Wolfgang Tillmann ◽  
Frank Walther ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Protective Coatings ◽  
Fatigue Behavior ◽  
Wind Waves ◽  
Offshore Wind ◽  
Coating Materials ◽  
Corrosive Media ◽  
Machine Hammer Peening ◽  
Hammer Peening ◽  
Compressive Residual Stresses

Structural elements of offshore facilities, e.g., offshore wind turbines, are subject to static and dynamic mechanical and environmental loads, for example, from wind, waves, and corrosive media. Protective coatings such as thermal sprayed ZnAl coatings are often used for protection, mainly against corrosive stresses. The Machine Hammer Peening (MHP) process is an innovative and promising technique for the post-treatment of ZnAl coating systems that helps reducing roughness and porosity and inducing compressive residual stresses. This should lead to an enhancement of the corrosion fatigue behavior. In this paper, the effect of a thermally assisted MHP process was investigated. The softening of the coating materials will have a direct effect on the densification, residual porosity and the distribution of cracks. The investigation results showed the influence of thermally assisted MHP on the surface properties, porosity, residual stresses, and hardness of the post-treated coatings. The best densification of the coating, i.e., the lowest porosity and roughness and the highest compressive residual stresses, were achieved at a process temperature of 300 °C. A further increase in temperature on the other hand caused a higher porosity and, in some cases, locally restricted melting of the coating and consequently poorer coating properties.

scholarly journals Effect of machine hammer peening on the surface integrity of a ZnAl-based corrosion protective coating

2020 ◽  
Vol 318 ◽  
pp. 01008
Author(s):  
Alina Timmermann ◽  
Mohamed Abdulgader ◽  
Leif Hagen ◽  
Alexander Koch ◽  
Philipp Wittke ◽  
...  
Keyword(s):  
Corrosion Fatigue ◽  
Surface Integrity ◽  
Protective Coatings ◽  
Fatigue Behavior ◽  
Turbine Blades ◽  
Fatigue Properties ◽  
Machine Hammer Peening ◽  
Coated Surfaces ◽  
Thermally Sprayed ◽  
Hammer Peening

Thermally sprayed protective coatings are applied onto many mechanically stressed components such as support structures, shafts, turbine blades or heat exchangers. In addition to the static or cyclic load, a superimposition with corrosion processes occurs in many cases. Thermal sprayed ZnAl coatings are known for their performant corrosion protection properties. Within this context, the potential of ZnAl-based layer systems was analyzed regarding corrosion fatigue behavior. Therefore, a timeand cost-efficient testing strategy based on a corrosion-superimposed load increase procedure was used to estimate the effects of a corrosive attack during cyclic loading. The investigated coating systems were thermally sprayed and partially post-processed with a Machine Hammer Peening (MHP) operation. This treatment was identified as an appropriate technique for compressing and smoothing coated surfaces. The inter-relationships between the parametrization of the MHP process, the resulting surface integrity, and the estimated corrosion fatigue properties were analyzed. The investigations indicate a positive effect of MHP post-processing operations on the surface properties of the ZnAl-based coating system.

Effects of Ultrasonic Deep Rolling on Fatigue Performance of Pre-Corroded 7A52 Aluminum Alloy

2011 ◽  
Vol 189-193 ◽  
pp. 897-900 ◽  
Author(s):  
Xiong Lin Ye ◽  
You Li Zhu ◽  
Dong Hu Zhang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Aluminum Alloys ◽  
Residual Stresses ◽  
Fatigue Behavior ◽  
Fatigue Performance ◽  
Deep Rolling ◽  
Fatigue Crack Nucleation ◽  
7A52 Aluminum Alloy ◽  
Compressive Residual Stresses

The effects of ultrasonic deep rolling (UDR) on the fatigue behavior of pre-corroded 7A52 aluminum alloys were investigated. By means of X-Ray diffraction stress measurements and scanning electron microscopy (SEM), residual stress and fractograph of 7A52 aluminum alloys with and without UDR treatment were analyzed. The results indicated that the UDR produced compressive residual stresses with depth approaching 1mm. UDR treatment can extend the fatigue life of the pre-corroded 7A52 specimens to a large extent, depending on the level of corrosion and UDR parameter. For the slightly corrode specimens, the UDR treatment changed the fatigue crack nucleation site from surface to the transition zone between the compressive residual stresses and tensile stresses, resulted in a much longer fatigue life. For the severely corrode specimens, the crack still nucleated by intergranular cracking, however, due to the compressive residual stresses introduced and the closure of the corrosion pits and corrosion micro-crocks, UDR treatment still improved fatigue performance of the pre-corroded 7A52 aluminum alloy substantially.

Surface Modification and Fatigue Behavior of High-Pressure Oil Jet-Peened Medium Carbon Steel, AISI 1040

2006 ◽  
Vol 129 (3) ◽  
pp. 601-606 ◽  
Author(s):  
A. Sahaya Grinspan ◽  
R. Gnanamoorthy
Keyword(s):  
High Pressure ◽  
Surface Modification ◽  
Carbon Steel ◽  
Residual Stresses ◽  
Fatigue Behavior ◽  
Optical Microscope ◽  
Medium Carbon Steel ◽  
Medium Carbon ◽  
Oil Jet ◽  
Compressive Residual Stresses

Introduction of compressive residual stresses on the fatigue-loaded components is one of the techniques followed to improve the fatigue life of industrial components. Oil jet peening is a surface modification process for the introduction of compressive residual stresses. A high-pressure oil jet is made to impinge on the surface to be peened. Preliminary studies were carried out on the medium carbon steel at the oil pressure of 50MPa. The compressive residual stress induced on the surface of unpeened and oil jet-peened AISI 1040 steel was 21MPa and 200MPa, respectively. Fully reversed cantilever bending fatigue behaviors of medium carbon steel in both under peened and unpeened conditions were evaluated at room temperature. Oil jet-peened specimens exhibited superior fatigue performance compared to the unpeened specimens. Fractographical analyses were carried out for specimens broken at several tested stress levels using optical microscope.

Fatigue Life Improvement Using Mechanical Post Treatment for Weldment

2008 ◽  
Vol 580-582 ◽  
pp. 97-100
Author(s):  
Seung Ho Han ◽  
Jeong Woo Han ◽  
Yong Yun Nam
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Quantitative Measure ◽  
Fatigue Strength Improvement ◽  
Weld Profile ◽  
Weld Toe ◽  
Life Improvement ◽  
Hammer Peening ◽  
Compressive Residual Stresses

Mechanical post treatments for welded structures have been applied in various industrial fields and, in most cases, have been found to cause substantial increase in their fatigue strength. These methods, generally, consist of the modification of weld toe geometry and the introduction of compressive residual stresses. In hammer peening, the weld profile is modified due to removal or reduction of minute crack-like flaws; compressive residual stresses are also induced by repeated hammering of the weld toe region with blunt-nosed chisel. In this study, a hammer peening procedure, using commercial pneumatic chipping hammer, was developed; a quantitative measure of fatigue strength improvement was performed. The fatigue life of hammer-peened specimen was prolonged by approximately 10 times in S=240MPa, and was doubled for the as-welded specimen.

scholarly journals On the Evolution of Residual Stresses, Microstructure and Cyclic Performance of High-Manganese Austenitic TWIP-Steel after Deep Rolling

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 825 ◽  
Author(s):  
Torben Oevermann ◽  
Thomas Wegener ◽  
Thomas Niendorf
Keyword(s):  
Residual Stresses ◽  
Cryogenic Temperature ◽  
Twip Steel ◽  
Fatigue Behavior ◽  
Deep Rolling ◽  
High Manganese ◽  
Near Surface ◽  
Number Of Cycles ◽  
Compressive Residual Stresses ◽  
Cycles To Failure

The mechanical properties and the near surface microstructure of the high-manganese twinning-induced plasticity (TWIP) steel X40MnCrAl19-2 have been investigated after deep rolling at high (200 °C), room and cryogenic temperature using different deep rolling forces. Uniaxial tensile tests reveal an increase in yield strength from 400 to 550 due to surface treatment. The fatigue behavior of selected conditions was analyzed and correlated to the prevailing microstructure leading to an increased number of cycles to failure after deep rolling. Deep rolling itself leads to high compressive residual stresses with a stress maximum of about 800 in the subsurface volume characterized by the highest Hertzian pressure and increased hardness up to a distance to the surface of approximately 1 mm with a maximum hardness of 475 0.1. Due to more pronounced plastic deformation, maximum compressive residual stresses are obtained upon high-temperature deep rolling. In contrast, lowest compressive residual stresses prevail after cryogenic deep rolling. Electron backscatter diffraction (EBSD) measurements reveal the development of twins in the near surface area independently of the deep rolling temperature, indicating that the temperature of the high-temperature deep rolling process was too low to prevent twinning. Furthermore, deep rolling at cryogenic temperature leads to a solid–solid phase transformation promoting martensite. This leads to inferior fatigue behavior especially at higher loads caused by premature crack initiation. At relatively low loads, all tested conditions show marginal differences in terms of number of cycles to failure.

Residual Stresses in Welded Joints after Different Mechanical Surface Treatments

2006 ◽  
Vol 524-525 ◽  
pp. 401-406
Author(s):  
Thomas Nitschke-Pagel ◽  
Hamdollah Eslami-Chalandar
Keyword(s):  
Residual Stresses ◽  
Welded Joints ◽  
Shot Peening ◽  
Depth Of Penetration ◽  
Fatigue Strength Improvement ◽  
Weld Toe ◽  
Cold Worked ◽  
Hammer Peening ◽  
Compressive Residual Stresses ◽  
Strength Improvement

Investigations on welded joints of a low strength steel and of an age-hardened aluminium- alloy have been performed to compare the effects of different post-weld treatment methods. The experimental results show, that the methods which are working with help of ultrasonic activation lead to a higher depth of penetration of the compressive residual stresses as shot peening does. The cold worked surface area is deeper and the hardening effect can be found in deeper layers. Furthermore the shape of the weld toe is changed strongly due to the cold working of the surface with the consequence of a change of the weld toe geometry. Anyway the fatigue strength improvement is comparable to that which is generated by shot peening (steel) or less than after shot peening (aluminium). The reason is, that the shape of the treated weld toe profile must not be necessarily smoother due to the ultrasonic hammer peening. Depending on the treatment parameters also sharp defects can be produced at the boarder of the treated zone which may compensate the beneficial effect of the compressive residual stresses.

scholarly journals Induction of Residual Stresses and Increase of Surface Hardness by Machine Hammer Peening Technology

2012 ◽  
pp. 0697-0702
Author(s):  
Beatrix Adjassoho ◽  
Ernst Kozeschnik ◽  
Christoph Lechner ◽  
Friedrich Bleicher ◽  
Stefan Goessinger ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Surface Hardness ◽  
Machine Hammer Peening ◽  
Hammer Peening

scholarly journals X-ray Determination of Compressive Residual Stresses in Spring Steel Generated by High-Speed Water Quenching

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1154
Author(s):  
Diego E. Lozano ◽  
George E. Totten ◽  
Yaneth Bedolla-Gil ◽  
Martha Guerrero-Mata ◽  
Marcel Carpio ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
High Speed ◽  
Spring Steel ◽  
X Ray Diffraction ◽  
Laboratory Equipment ◽  
X Ray ◽  
Water Chamber ◽  
Hardened Case ◽  
Compressive Residual Stresses

Automotive components manufacturers use the 5160 steel in leaf and coil springs. The industrial heat treatment process consists in austenitizing followed by the oil quenching and tempering process. Typically, compressive residual stresses are induced by shot peening on the surface of automotive springs to bestow compressive residual stresses that improve the fatigue resistance and increase the service life of the parts after heat treatment. In this work, a high-speed quenching was used to achieve compressive residual stresses on the surface of AISI/SAE 5160 steel samples by producing high thermal gradients and interrupting the cooling in order to generate a case-core microstructure. A special laboratory equipment was designed and built, which uses water as the quenching media in a high-speed water chamber. The severity of the cooling was characterized with embedded thermocouples to obtain the cooling curves at different depths from the surface. Samples were cooled for various times to produce different hardened case depths. The microstructure of specimens was observed with a scanning electron microscope (SEM). X-ray diffraction (XRD) was used to estimate the magnitude of residual stresses on the surface of the specimens. Compressive residual stresses at the surface and sub-surface of about −700 MPa were obtained.

scholarly journals Thermal Effects on Surface and Subsurface Modifications in Laser-Combined Deep Rolling

2021 ◽  
Vol 5 (2) ◽  
pp. 55
Author(s):  
Robert Zmich ◽  
Daniel Meyer
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Thermal Loads ◽  
Deep Rolling ◽  
Mechanical Loads ◽  
Thermomechanical Process ◽  
Compressive Stresses ◽  
New Process ◽  
Negative Effect ◽  
Compressive Residual Stresses

Knowledge of the relationships between thermomechanical process loads and the resulting modifications in the surface layer enables targeted adjustments of the required surface integrity independent of the manufacturing process. In various processes with thermomechanical impact, thermal and mechanical loads act simultaneously and affect each other. Thus, the effects on the modifications are interdependent. To gain a better understanding of the interactions of the two loads, it is necessary to vary thermal and mechanical loads independently. A new process of laser-combined deep rolling can fulfil exactly this requirement. The presented findings demonstrate that thermal loads can support the generation of residual compressive stresses to a certain extent. If the thermal loads are increased further, this has a negative effect on the surface layer and the residual stresses are shifted in the direction of tension. The results show the optimum range of thermal loads to further increase the compressive residual stresses in the surface layer and allow to gain a better understanding of the interactions between thermal and mechanical loads.

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