Microstructure and mechanical property of Ti and Ti6Al4V prepared by an in-situ shot peening assisted cold spraying

• An in-situ shot peening assisted cold spraying is developed.
• Large sized shot peening particles are mixed into the spraying powders.
• Nitrogen at only 550 °C is used as the processing gas.
• Porosity of Ti and TC4 coatings is decreased to 0.3% and 0.6%, respectively.
• Deposition efficiency is not remarkably influenced by the in-situ shot peening.

In the current study, for the first time, an in-situ shot peening (SP) is introduced into cold spray by mixing large sized stainless steel particles with spraying powders to prepare dense Ti6Al4V (TC4) and commercially pure Ti (CP Ti) deposits. It is attempted that via the in-situ hammering by these large sized SP particles, plastic deformation of the previously deposited layers could be greatly enhanced and thereby porosities can be declined. Results show that, as the SP particle proportion increases from 0 to 70 vol.%, porosities of the CP Ti and TC4 coatings decrease from 13.7% and 15.3% to 0.3% and 0.7%, respectively. SEM observations reveal that no SP particle is incorporated into TC4 coatings. A few SP particles (≤ 2.3 vol.%) are observed in CP Ti coatings due to the relatively low hardness of CP Ti. Only a slight decline trend in deposition efficiency of the CP Ti and TC4 powders is detected as increasing SP content. The in-situ SP results in remarkable work hardening. As the SP particle content increases from 0 to 70 vol.%, Vickers microhardness of the CP Ti and TC4 coatings increase from ~ 143 and 240 HV0.3 to ~ 203 and 427 HV0.3, respectively.

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