Laser deposition technology assisted by friction stir processing for preparation of nanostructured Fe-Cr-Si alloy layer

Although laser deposition has found its widespread applications in materials manufacture, this technology has been significantly limited by the associated metallurgical defects, such as pores, brittle phase precipitation along grain boundary during the laser melting/solidification process. In this paper, we used a novel laser deposition technology assisted by friction stir processing (FSP) to eliminate these common metallurgical defects. A Fe-Cr-Si alloy was selected as a representative material. Severe plastic deformation caused by FSP has refined the coarse solidification microstructure into ultrafine grained or even nano-grained microstructure on the top surface of the Fe-Cr-Si samples. Meanwhile, the large and interconnected Fe-Cr intermetallics precipitates were broken down to nanoparticles. The refinement of both primary grains and intermetallic particles results in an increase of microhardness from 640 HV to above 700 HV and a decrease of wear rate from 4.8 × 10−14 to 3.2 × 10−14 mm3/m.