Marginalized Layer Strength Improvement in Brittle Materials through Shot Peening

© Photo Felizitas Gemetz / Fraunhofer IWM

Shot peening is a widely used surface treatment to improve the static and cyclical strength of metal components. It is utilized in the mechanical stabilization of edge layers and for incorporation of more advantageous residual stresses. Shot peening is generally viewed as detrimental regarding brittle materials and is therefore not utilized. Experience has shown that in room temperature, brittle materials such as ceramic break as opposed to deforming. Experiments on brittle ceramic materials carried out at the Fraunhofer IWM have shown that under precise boundary conditions shot peening can yield high compressive residual stress to over 2 GPa. This allows for drastic improvements to near surface strength characteristics in ceramic, hard metal and hard-chrome layer components, as well as warp balancing and thin-walled parts to be formed without cutting. 

 

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Implementation of feasibility studies

Determination of optimal shot peening parameters

Residual stress experiments

Determination of edge layer strength properties including hardness, dislocation density fracture toughness

Determination of applied strength characteristics including static and cyclical load bearing capacity

Low volume production treatments

Experiments concerning straightening and shot peening shaping 

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Examples

© Photo Fraunhofer IWM

Residual stress in ceramic and hard metal after shot blasting

© Photo Fraunhofer IWM

Inhibited crack formation in ceramic and hard chrome after shot peening

© Photo Fraunhofer IWM

Left: Compensation of defects in ceramic bearing rollers through shot blasting Right: Increasing the service life of carbide drills through shot peening

Literature

Pfeiffer, W.; Wenzel, J.; Shot peening of brittle materials – status and outlook; Material Science Forum 638-642 (2010) 799-804 Link

Pfeiffer, W.; Gumbsch, P.; Strengthening of silicon nitride ceramics by shot peening; International journal of materials research 97/12 (2006) 1673-1678 Link

Pfeiffer, W.; Koplin, C.; Reisacher, E.; Wenzel, J.; Residual stresses and strength of hard chromium coatings; Materials Science Forum 681 (2011) 133-138; Link

Pfeiffer, W.; Höpfel, H., Peen forming of ceramics - a new chipless shaping technique, Developments in Strategic Materials and Computational Design V: A Collection of Papers Presented at the 38th International Conference on Advanced Ceramics and Composites 2014, Ceramic engineering and science proceedings 35/8; Kriven, W.M.; Zhu, d.; Moon, K.I.; Hwang, T.; Wang, J.; Lewinsohn C.; Zhou, Y. (Eds.); John Wiley & Sons, Inc., Hoboken, NJ, USA (2015) 229-236 Link

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