Key objectives
- Investigate the suitability of the laser cladding process shown in Figure 1 for repair of wheel-seat areas on axles.
- Produce laser-engineered coatings with high fatigue, wear, adhesion and corrosion performance for refurbishment of locomotive axles and other assets.
- Assess the mechanical properties of coated samples.
- Develop a reliable means of inspecting various coatings.
Close collaboration
Wall Colmonoy developed and produced a number of powders with varying compositions for analysis by the consortium. This analysis involved assessing the bond quality resulting from each powder and comparing the mechanical properties to those of the parent material. LASE produced a variety of coupon samples (Figure 2), using a range of cladding parameters to support a parametric study. TWI subsequently carried out X-ray computer tomography (XCT) inspection to produce images such as those shown in Figures 3 and 4 to support the assessment of coating quality, defect characterisation and down-selection of coupons for fatigue testing. These results informed the development of an equivalent but more portable ultrasonic inspection technique.
By optimising the coating process of the selected powders, defects such as cracking, voiding, porosity and lack of fusion were minimised. The fatigue testing of the best coupons enabled the comparison of the mechanical performance of cladded coupons with coupons of parent material.
Conclusion
The project successfully proved the application of a laser-engineered coating to rail axles, and demonstrated its performance through destructive and non-destructive means. The process demonstrated a cost-effective way of refurbishing axles which would otherwise be scrapped due to wear or corrosion. Further work will focus on the continued assessment and refinement of various powders and process parameters for commercialisation in a wider range of applications.