Erosion testing of laser-cladding layers by abrasive water-jetting

Abstract

Laser cladding is an advanced technique to improve the erosion resistance of the surface of parts. The erosion testing of five laser-cladding layers (METCO 81NS, METCO 430NS, SM 5847, HF147, AMDRY 302) was studied using three-axis CNC (computer numerical control) abrasive water-jetting (AWJ) at various erosion times t and various impingement angles α. An indicator named erosion rate E was defined to calculate and evaluate the erosion resistance of the laser-cladding layers. The effects of erosion time t and impingement angle α on the erosion of the five cladding layers were discussed. It is shown by calculation that SM 5847 has the best erosion resistance, and METCO 81NS has the worst erosion resistance among the five cladding layers. The erosion mechanisms for the five cladding layers were studied according to the surface morphologies of the eroded cladding layers. There exist two kinds of erosion mechanisms about the erosion of the cladding layers. One is brittle fracture mechanism; another is deformation wear mechanism. METCO 430NS has interconnected cracks after erosion; the brittle fracture mechanism is dominant. Both the brittle fracture mechanism and the deformation wear mechanism contribute to the erosion of METCO 81NS because of some discrete cracks in the eroded cladding layer. For SM 5847, HF147, and AMDRY 302, the deformation wear mechanism is absolutely dominant due to no cracks in these eroded cladding layers. The stress state of a cladding layer during the erosion process also has an effect on the erosion rate. Compared with a cladding layer subject to deformation wear, the normal stress perpendicular to the eroded surface has a greater effect on the erosion rate of a cladding layer subject to brittle fracture. Compared with grit blasting, AWJ can reduce the grit embedding in the target material due to the action of the high-pressure water, therefore improving the precision of erosion testing. The erosion testing is numerically controlled by a three-axis CNC system. Therefore, precise and detailed results at various parameters can be obtained.