Effect of shot peening on the residual stress and mechanical behaviour of low-temperature and high-temperature annealed martensitic gear steel 18CrNiMo7-6

A martensitic gear steel (18CrNiMo7-6) was annealed at 180 °C for 2h and at ∼ 750 °C for 1h to design two different starting microstructures for shot peening. One maintains the original as-transformed martensite while the other contains irregular-shaped sorbite together with ferrite. These two mater...

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Bibliographic Details
Published in:IOP conference series. Materials Science and Engineering 2017-07, Vol.219 (1), p.12046
Main Authors: Yang, R, Zhang, X, Mallipeddi, D, Angelou, N, Toftegaard, H L, Li, Y, Ahlström, J, Lorentzen, L, Wu, G, Huang, X
Format: Article
Language:English
Subjects:
Annealing
Ferrite
High temperature
Low temperature
Martensitic stainless steels
Martensitic transformations
Mechanical properties
Microhardness
Microstructure
Nickel chromium molybdenum steels
Optical properties
Residual stress
Shot peening
Sorbite
Tempered martensite
Tensile tests
X ray sources
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Summary:A martensitic gear steel (18CrNiMo7-6) was annealed at 180 °C for 2h and at ∼ 750 °C for 1h to design two different starting microstructures for shot peening. One maintains the original as-transformed martensite while the other contains irregular-shaped sorbite together with ferrite. These two materials were shot peened using two different peening conditions. The softer sorbite + ferrite microstructure was shot peened using 0.6 mm conditioned cut steel shots at an average speed of 25 m/s in a conventional shot peening machine, while the harder tempered martensite steel was shot peened using 1.5 mm steel shots at a speed of 50 m/s in an in-house developed shot peening machine. The shot speeds in the conventional shot peening machine were measured using an in-house lidar set-up. The microstructure of each sample was characterized by optical and scanning electron microscopy, and the mechanical properties examined by microhardness and tensile testing. The residual stresses were measured using an Xstress 3000 G2R diffractometer equipped with a Cr Kα x-ray source. The correspondence between the residual stress profile and the gradient structure produced by shot peening, and the relationship between the microstructure and strength, are analyzed and discussed.
ISSN:1757-8981
1757-899X
1757-899X
DOI:10.1088/1757-899X/219/1/012046