**Acknowledgements**

after SP. In fact, rolling contact fatigue tests carried out by Ohba et al. [30] showed nearly equal fatigue lives for ground as-austempered DI and SP ADI using shots with a diameter of 0.1 mm. On the other hand, Vrbka et al. [46] report a deterioration in the rolling contact fatigue resistance of steel despite the use of shots having smaller diameters of 0.07 and 0.11 mm. One notes that shots used in the present study had diameters in the range of 0.85–1.2 mm. Results in this study [46] were improved when testing specimens, which were polished after SP, thus creating relatively smoother surfaces, in which the asperities did not protrude the lubricant film. However, grinding or polishing of SP surfaces might be challenging since extra care must be taken so as not to remove the SP layer and hence eliminate the beneficial effects, which result

The work presented in this chapter has hopefully contributed to a better understanding of the mechanical behaviour and tribological characteristics of both as-austempered ductile iron (ADI) and shot-peened (SP) ADI. A case study was presented in which bending fatigue tests and three different tribological tests were carried out on Cu-Ni-alloyed ADI. The major con-

**1.** After SP, a good balance between surface roughness, high surface hardness and hardened depth was obtained. Austenite transformed to martensite by the TRansformation Induced Plasticity (TRIP) phenomenon and the surface hardness increased by about 43% to a value of approximately 535 HV; the depth of the SP layer was approximately 400 μm, residual compressive stresses had a maximum value of 975 MPa and the surface roughness

**2.** Rotating bending fatigue tests revealed that SP improved the bending fatigue strength of the Cu-Ni ADI by around 60% from 250 to 390 MPa. This was attributed to the induced compressive stresses that shift crack nucleation to the sub-surface and hinders fatigue

**3.** Dry lubricated sliding wear tests showed that SP did not result in an improvement in the dry sliding wear resistance of Cu-Ni ADI. The potential advantages resulting from the higher hardness at the surface, stress-induced austenite to martensite transformation and the residual compressive stresses of the SP specimens are counteracted by the induced

**4.** Starved lubricated sliding wear tests showed that SP resulted in an 800% improvement in the scuffing wear resistance of the ADI. The lower resistance to scuffing attested by the as-austempered specimens was attributed to plastic flow and micro-fracture of asperities. On the other hand, the superposition of indentations arising from the SP process acted as oil reservoirs and hence reduced surface traction forces. The higher scuffing resistance of the SP specimens was also partly attributed to the high hardness and high compressive

from SP (high hardness and compressive stresses at the surface).

**4. Conclusion**

40 Advanced Surface Engineering Research

clusions of can be summarised as follows:

increased from 0.4 to 3.1 μm.

crack propagation.

surface roughness.

stresses present in the surface of these specimens.

The authors would like to acknowledge the positive impact of ERDF funding and the purchase of the testing equipment through the project: Developing an Interdisciplinary Material Testing and Rapid Prototyping R&D Facility (Ref. no. 012).
