Effect of Machining and Shot Peening on the Residual Stresses of Superalloy Turbine Discs

1995 ◽  
Author(s):  
Federica Taricco
Keyword(s):  
Residual Stresses ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Thermal Conditions ◽  
Production Costs ◽  
Quality Level ◽  
Machining Parameters ◽  
Stress Distributions ◽  
Inconel 718 Superalloy ◽  
Engine Components

It is well known that the field of residual stresses in the surface layer of a component greatly influences its fatigue behavior. The distribution of stresses is created by processes like welding, machining, thermal treatments. The object of the present study was to correlate the effect of operations like turning, broaching and shot peening with the residual stresses of a highly–stressed flight safety component like a turbine disc made in Inconel 718 superalloy. The residual stress distributions were measured with newly installed x–ray diffraction equipment, in which real engine components can be tested. Different machining parameters and tools were used, and other factors like deformations during processing and thermal conditions of the disc in service were taken into account. The final aim of the activity was to perform a manufacturing cycle which can minimize production costs and, at the same time, guarantee the highest possible quality level required in such a critical component.

scholarly journals Influence of Shot Peening on the Isothermal Fatigue Behavior of the Gamma Titanium Aluminide Ti-48Al-2Cr-2Nb at 750 °C

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1083
Author(s):  
Christoph Breuner ◽  
Stefan Guth ◽  
Elias Gall ◽  
Radosław Swadźba ◽  
Jens Gibmeier ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Shot Peening ◽  
Elevated Temperatures ◽  
Stress Amplitude ◽  
Negative Impact ◽  
Fatigue Behavior ◽  
Surface Hardness ◽  
Fatigue Tests ◽  
Positive Effects ◽  
Isothermal Fatigue

One possibility to improve the fatigue life and strength of metallic materials is shot peening. However, at elevated temperatures, the induced residual stresses may relax. To investigate the influence of shot peening on high-temperature fatigue behavior, isothermal fatigue tests were conducted on shot-peened and untreated samples of gamma TiAl 48-2-2 at 750 °C in air. The shot-peened material was characterized using EBSD, microhardness, and residual stress analyses. Shot peening leads to a significant increase in surface hardness and high compressive residual stresses near the surface. Both effects may have a positive influence on lifetime. However, it also leads to surface notches and tensile residual stresses in the bulk material with a negative impact on cyclic lifetime. During fully reversed uniaxial tension-compression fatigue tests (R = −1) at a stress amplitude of 260 MPa, the positive effects dominate, and the fatigue lifetime increases. At a lower stress amplitude of 230 MPa, the negative effect of internal tensile residual stresses dominates, and the lifetime decreases. Shot peening leads to a transition from surface to volume crack initiation if the surface is not damaged by the shots.

scholarly journals Dealing with Uncertainties in Fatigue Strength Using Deep Rolling

2021 ◽  
pp. 93-103
Author(s):  
Berkay Yüksel ◽  
Mehmet Okan Görtan
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Rolling Direction ◽  
Longitudinal Direction ◽  
Tangential Direction ◽  
Deep Rolling ◽  
Longitudinal Rolling ◽  
6082 Aluminum Alloy

AbstractMechanical properties inherently possess uncertainties. Among these properties, fatigue behavior data generally shows significant scatter which introduces a challenge in the safe design of dynamically loaded components. These uncertainties in fatigue behavior are mainly results of factors related to surface state including: Roughness, tensile residual stresses, scratches and notches at surface. Therefore, controlling these parameters allows one to increase fatigue strength and reduce scatter and uncertainties in fatigue behavior. Mechanical surface treatments are applied on parts to increase fatigue strength via introducing compressive residual stresses and work-hardening at surface. Two of the most common among these treatments are shot peening and deep rolling. Shot peening has found many applications in industry because of its flexibility. However, it introduces irregularities at the surface and may increase roughness which causes uncertainties in the fatigue behavior data; especially for low-medium strength materials. Unlike shot peening, deep rolling reduces surface roughness. Therefore, it has the capability to reduce uncertainty in the fatigue behavior. To this date, rolling direction of deep rolling was selected as tangential direction to turning direction for axisymmetric parts. Nonetheless, the authors believe that the rolling direction has an apparent effect on the fatigue behavior. In this study, longitudinal direction was also applied for deep rolling operation and the results of these two direction applications on the EN-AW-6082 aluminum alloy were investigated. It was shown that, longitudinal rolling had yielded less scatter and uncertainty in the fatigue behavior than the tangential rolling together with the higher fatigue strength.

A Micromechanical Approach to Model Residual Stress Relaxation and Fatigue Crack Nucleation in High Strength Gear Steels

2007 ◽  
Author(s):  
Rajesh Prasanna ◽  
David L. McDowell
Keyword(s):  
Fatigue Crack ◽  
Residual Stresses ◽  
Shot Peening ◽  
Thermal Loading ◽  
Crack Nucleation ◽  
Fatigue Behavior ◽  
High Strength ◽  
Operating Conditions ◽  
Fatigue Crack Nucleation ◽  
Shock Peening

It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Of particular interest here are the residual stresses induced through shot peening process. Compressive residual stresses of high magnitudes are induced at and near the surface during shot peening process by virtue of constrained plastic deformation. These stresses enhance the service life of component by resisting fatigue crack nucleation and growth on surface of the specimen. Unfortunately, these residual stresses can relax significantly due to subsequent mechanical and/or thermal loading even under normal operating conditions.

Long Life Fatigue Behavior of Shot Peened Steels

2014 ◽  
Vol 627 ◽  
pp. 9-12
Author(s):  
Alan Plumtree
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Shot Peening ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Initiation Site ◽  
Cyclic Softening ◽  
Surface Layers ◽  
Long Life ◽  
Effect Of Surface

The fully reversed long life fatigue cycle behaviour of shot peened steels has been investigated. In the case of air cooled forged 0.4%C and 0.7%C steels, shot peening resulted in a relatively small effect on fatigue life (+2.2% and-2.0% respectively) owing to cyclic softening. Fatigue cracks in the shot peened specimens have been observed to initiate in sub-surface layers, reducing the detrimental effect of surface roughness. Neither cyclic softening nor hardening occurred in the smooth non shot peened samples cycled under the same conditions. Shot peening quench and tempered 0.5%C steel samples resulted in a reduced fatigue limit of 12.0% due to cyclic softening. Relaxation of the residual stresses occurred quickly in these steels due to adjustment and rebalancing of the residual stresses caused by the plastic strain. The effect of cyclic softening and shift in crack initiation site rather than the residual peening stresses was significant in determining the fatigue life of these shot peened steels.

scholarly journals Study of ultrasonic vibration–assisted thread turning of Inconel 718 superalloy

2019 ◽  
Vol 11 (10) ◽  
pp. 168781401988377
Author(s):  
Yu He ◽  
Zhongming Zhou ◽  
Ping Zou ◽  
Xiaogang Gao ◽  
Kornel F Ehmann
Keyword(s):  
Surface Quality ◽  
Ultrasonic Vibration ◽  
Inconel 718 ◽  
Gas Turbines ◽  
Tool Path ◽  
Machining Parameters ◽  
Thread Cutting ◽  
Workpiece Surface ◽  
Inconel 718 Superalloy ◽  
The Relationship

With excellent properties, high-temperature superalloys have become the main application materials for aircraft engines, gas turbines, and many other devices. However, superalloys are typically difficult to machine, especially for the thread cutting. In this article, an ultrasonic vibration–assisted turning system is proposed for thread cutting operations in superalloys. A theoretical analysis of ultrasonic vibration–assisted thread cutting is carried out. An ultrasonic vibration–assisted system was integrated into a standard lathe to demonstrate thread turning in Inconel 718 superalloy. The influence of ultrasonic vibration–assisted machining on workpiece surface quality, chip shape, and tool wear was analyzed. The relationship between machining parameters and ultrasonic vibration–assisted processing performance was also explored. By analyzing the motion relationship between tool path and workpiece surface, the reasons for improved workpiece surface quality by ultrasonic vibration–assisted machining were explained.

Measurement of Residual Stresses in Linear Friction Welded In-Service Inconel 718 Superalloy

2016 ◽  
Vol 879 ◽  
pp. 1800-1806 ◽  
Author(s):  
M. Smith ◽  
L. Bichler ◽  
D. Sediako
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Base Material ◽  
Peak Stress ◽  
Weld Interface ◽  
Aerospace Alloys ◽  
Aero Engine ◽  
Linear Friction ◽  
Inconel 718 Superalloy ◽  
Residual Strains

Measurement of residual strains by neutron diffraction of linear friction welded Inconel® 718 (IN 718) superalloy acquired from a mid-service aero-engine disk was undertaken in this study. Residual strain and stress throughout the various weld regions including the heat affected zone (HAZ), thermomechanical affected zone (TMAZ) and dynamically recrystallized zone (DRX) were characterized. The residual stresses were observed to increase from the base material to the weld interface, with a peak stress at the weld interface in all orthogonal directions. The trends for residual stress across the weld are in agreement with other work published in literature for solid state welding of aerospace alloys, where high residual stresses were commonly reported at the weld interface.

Instability Parameter for Machined Parts

1983 ◽  
Vol 105 (3) ◽  
pp. 133-136 ◽  
Author(s):  
A. Israeli ◽  
J. Benedek
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Single Point ◽  
Machining Parameters ◽  
Machining Processes ◽  
Etching Technique ◽  
Parametric Relationship ◽  
Machined Parts ◽  
Instability Parameter ◽  
Stress Profiles

The production of precision parts requires manufacturing processes which produce low residual stresses. This study was designed to investigate the parametric relationship between machining processes and residual stress distribution. Sets of steel specimens were single point turned at different feeds. The residual stress profiles of these specimens were monitored, using a continuous etching technique. A “Specific Instability Potential” parameter, derived from the strain energy of the residual stresses, was found to relate directly to the machining parameters. It is suggested that the Specific Instability Potential can be used as a parameter for specifying processing operations.

scholarly journals Study of the Turning Nickel Base Alloy Pyromet® 31V (SAE HEV8)

2011 ◽  
Vol 278 ◽  
pp. 312-320 ◽  
Author(s):  
Marcos Valério Ribeiro ◽  
André Luís Habib Bahia
Keyword(s):  
Thermal Conductivity ◽  
Mechanical Strength ◽  
High Temperatures ◽  
Base Alloy ◽  
Production Costs ◽  
Machining Parameters ◽  
Nickel Base Alloy ◽  
Low Thermal Conductivity ◽  
Nickel Base ◽  
Coated Carbide

Considering the constant technological developments in the aeronautical, space, automotive, shipbuilding, nuclear and petrochemical fields, among others, the use of materials with high strength mechanical capabilities at high temperatures has been increasingly used. Among the materials that meet the mechanical strength and corrosion properties at temperatures around 815 °C one can find the nickel base alloy Pyromet® 31V (SAE HEV8). This alloy is commonly applied in the manufacturing of high power diesel engines exhaust valves where it is required high resistance to sulphide, corrosion and good resistance to creep. However, due to its high mechanical strength and low thermal conductivity its machinability is made difficult, creating major challenges in the analysis of the best combinations among machining parameters and cutting tools to be used. Its low thermal conductivity results in a concentration of heat at high temperatures in the interfaces of workpiece-tool and tool-chip, consequently accelerating the tools wearing and increasing production costs. This work aimed to study the machinability, using the carbide coated and uncoated tools, of the hot-rolled Pyromet® 31V alloy with hardness between 41.5 and 42.5 HRC. The nickel base alloy used consists essentially of the following components: 56.5% Ni, 22.5% Cr, 2,2% Ti, 0,04% C, 1,2% Al, 0.85% Nb and the rest of iron. Through the turning of this alloy we able to analyze the working mechanisms of wear on tools and evaluate the roughness provided on the cutting parameters used. The tests were performed on a CNC lathe machine using the coated carbide tool TNMG 160408-23 Class 1005 (ISO S15) and uncoated tools TNMG 160408-23 Class H13A (ISO S15). Cutting fluid was used so abundantly and cutting speeds were fixed in 75 and 90 m/min. to feed rates that ranged from 0.12, 0.15, 0.18 and 0.21 mm/rev. and cutting depth of 0.8mm. The results of the comparison between uncoated tools and coated ones presented a machined length of just 30% to the first in relation to the performance of the second. The coated tools has obtained its best result for both 75 and 90 m/min. with feed rate of 0.15 mm/rev. unlike the uncoated tool which obtained its better results to 0.12 mm/rev.

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