Microstructure and nanoindentation hardness of shot-peened ultrafine-grained low-alloy steel
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The effect of shot peening (SP) on microstructure and hardness of ultrafine-grained (UFG) low-alloy steel was investigated. With increasing shot-peening time from 0.5 to 1.5 h, grain size of UFG low-alloy steel decreases from 400 to 280 nm at surface whilst that of the layer with a depth of 160 μm decreases from (230 ± 15) to (75 ± 5) nm. Interestingly, nanoindentation shows that hardness increases linearly with increasing the SP duration, reaching a value as high as (7.10 ± 0.1) GPa at the depth of 160 µm after the SP duration of 1.5 h. The thickness of the SP treated layer is measured as ~ 300 μm. The Hall–Petch (H–P) relationship was established for the hardening layer. Correspondingly, abrasion resistance should be ~ 51% higher than that of as-prepared UFG low-alloy steel. As shown in SP processing, grain refinement is the key factor responsible for the strengthening of the studied steel.
KeywordsLow-alloy steel Shot peening Grain refinement Nanoindentation Hardness
This project was supported by NSAF (Grant No. U1430132), the National Natural Science Foundation of China (NSFC) (Grant No. 51574079), and the Science and Technology Research Project of Education Department of Liaoning Province (L20150177).
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