Effect of Ti and TiC additions on the microstructure and wear resistance of high chromium white irons produced by laser directed energy deposition

Laser directed energy deposition (L-DED) is an additive technology that offers a rapid solution for repairing mining components made of High Chromium White Iron (HCWI) on site. However, the refined carbide morphology from the rapid cooling in L-DED is detrimental to the wear resistance of the repairs. In this study, two types of powder (Ti powder and TiC powder) were added to improve the wear resistance of L-DED HCWI. The Ti powder addition promoted the formation of in-situ TiC while the TiC powder addition resulted in coarse ex-situ TiC and fine in-situ TiC in the as-deposited microstructure. The addition of both powders destabilised the austenitic matrix (gamma-Fe). The wear resistance was investigated by a high stress abrasion test using silica sand (softer than M7C3) and a pin-on-disk wear test using a ruby pin (significantly harder than M7C3). The best wear results were achieved with 6.55 wt% Ti powder addition. This destabilised gamma-Fe in the as-deposited micro-structure which underwent strain-induced martensite formation during the high stress abrasion wear testing, improving the wear resistance of the alloy. The addition of TiC powder improved the wear resistance in the high stress abrasion test due to the increase in the fraction of carbide. In the pin-on-disk wear test, the alloys with TiC powder addition performed better than the cast sample because a greater amount of gamma-Fe matrix in the micro-structure provided a better combination of hardness and ductility.

Automated summary

Laser directed energy deposition (L-DED) is an additive technology used for repairing mining components made of High Chromium White Iron (HCWI) on site. The addition of Ti powder and TiC powder to L-DED HCWI improved wear resistance, with Ti powder promoting in-situ TiC formation and TiC powder increasing the fraction of carbide and the amount of gamma-Fe matrix, leading to better wear resistance in high stress abrasion and pin-on-disk wear tests.