Shot peening using an air blast machine at elevated temperatures

With a new system shot peening using an air blast machine at elevated tempe ratures is feasable. This is done by mixing the cold airflow which contains the peening media with a hot airflow heated up with a flow heating system. It will be shown for a quenched and tempered steel 42 CrMo 4 (equivalent t o AISI 4140) that the fatigue strength increases with increasing peening te mperature T-peen in the temperature range 20 degrees C less than or equal t o T-peen < 290 degrees C. On the one hand this is caused by slightly higher compressive residual stresses in the near surface area which is influenced by the shot peening process. On the other hand different dislocation struc tures are generated as a result of strain ageing which occurs while and aft er the shot peening treatment. This also causes a higher stability of the r esidual stresses compared to the conventional shot peening.