Surface strengthening aluminum alloy by in-situ TiC-TiB2 composite coating

Abstract

An integration technology was employed to prepare TiC-TiB2 strengthening coating on aluminum alloys, with the combination of Self-propagating high-temperature synthesis (SHS) and Vacuum-expendable pattern casting (VEPC). During the VEPC process, the Ti-C-B4C-TP SHS reaction was ignited by molten Al alloy, resulting in the simultaneous obtainment of TiC-TiB2 SHS coating with the cast Al alloy. Specifically, Teflon (PTFE) as reaction promoter was introduced into the SHS system to guarantee the reaction to be ignited successfully. With 3.8 wt% PTFE addition, homogeneous and dense TiC-TiB2 coating microstructure was obtained. Compared to the matrix, the hardness of the surface coating increased from 80 HB to 284 HB. And, the weight loss decreased from 533 mg to 52 mg at load of 20 N, indicating the significant improvement of wear resistance. In addition, a comprehensive bonding strength of 160 MPa was achieved. The proposed method for preparing hard coating on Al alloys broadens their industry application, where higher hardness and better wear resistance are required.