The Effect of Laser Treatment on The Erosion Resistance of a CU-NI Austempered DuctileIron

Abstract

The present work investigates the effect of laser surface hardening on the erosion resistanceofalloyedaustempered ductile iron (1.5% copper and 1.5% nickel)austenitized for different austenitising times.
Continuous wave of Co2 laser was used to heat by overlapping technique .The laser processing parameters used were ;(1000) w,laser power,(1000) mm\min. Scanning speed and (40) L\min. Argon flow rate .
After laser treatments erosion tests were carried out on the untreated and laser treated samples surfaces. The erodent particles used were pressurized silica (+300 to 500) flow at speed of (50 m\sec). The erosion tests were performed at different angles (30°, 60°and 90°).
Erosion tests showed significant reduction in the erosion rate after laser treatment at all impinging angles. Erosion resistance is improved depending on the impingement angle, (weight losses in grams at 90° > weight losses in grams at 60° > weight losses in grams at 30°). Increasing the impingement angle increases the erosion rate for both untreated and laser treated samples. The erosion mechanism was studied by SEM observation of the fracture surface. In the untreated samples the erosion was mainly by sever plastic deformation , micro-ploughing and micro-cutting while in laser treated samples ,it was by localized strain at the over lapped regions which leads to crack formation that eventually leads to fracture . This improvement in erosion resistance was attributed to the fine and homogenous structure, high hardness and the elimination of graphite nodules which were the source of notches.