Shot peen to work harden the surface in order to improve wear properties

Many materials can be work hardened from Steels, Inconel Alloys, Titanium and Aluminium alloys. This is particularly useful where it is not practical to heat treat a component due to size or complexity. Shot peening can be used to locally work harden specific areas or it can be applied to the whole component.

The graph opposite (scroll to view) shows what can typically be achieved by shot peening stainless steels.

As can be seen the alloy 304 has considerably more hardenability due to the effect of shot peening which transforms approximately 50% of the Austenite to Martensite.

The 316 does not as easily transform to martensite owing to the additional Nickel and Molybdenum which stabilises the Austenite. As a note the Martensitic transformation will make the material magnetic from a nonmagnetic Austenitic state.

Transformations Induced in
Austenitic Steels by Shot Peening
D Kirk, N.J. Payne Coventry University

Work Hardening of Inconel 718 by Shot Peening

Inconel 718 work hardening

Inconel is another alloy that responds well to work hardening by shot peening.

As can be seen in the graph at 200% coverage the Microhardness increases by 60% with high energy shot peening.