Comparative study on the reinforcement effects of WC and TiC in the laser cladding layer of Ti-6Al-4V alloy

Abstract

Addressing the unclear evolutionary process and characteristics of TiC and WC morphologies in Ti-6Al-4V (TC4) alloy cladding layers, as well as the unelucidated mechanisms and behaviors of their strengthening precipitates, we prepared x wt% TiC + (1-x) wt% TC4 cladding layers and x wt% WC + (1-x) wt% TC4 cladding layers (x = 10, 15, and 20) on the surface of TC4 alloy using an optimized laser cladding process. We analyzed and compared the influence of the two types of carbide reinforcements on the phase composition of the cladding layers, and elucidated the strengthening mechanisms, precipitation behavior and characteristics, as well as the presence and distribution of the two carbide reinforcements within the cladding layers. The study also compared the effects of varying reinforcement contents on the microhardness, wear resistance, and electrochemical corrosion resistance of the cladding layers. The experimental results show that WC has a significant impact on the phase composition of the cladding. In the TiC cladding layer, only the TiC phase is newly added, while in the WC cladding layer, new phases such as WC, W₂C, W and (Ti, W)C_1-x are formed. TiC exists mainly in two forms, molten and unmelted, in the cladding. The molten TiC precipitates from the molten pool in petal-like and granular forms and is evenly distributed in the cladding. WC mainly exists in an unmelted state in the cladding and is deposited in large quantities at the bottom of the cladding. The average microhardness of the 20 wt% TiC cladding is 92 % of that of the 20 wt% WC cladding. However, its friction and wear rate is only 41 % of that of the latter, and its electrochemical corrosion rate is merely 20 % of that of the 20 wt% WC cladding. We recommend using a 20 wt% TiC +80 wt% TC4 ratio under a laser power of 2500 W, a scanning speed of 5 mm/s, and a powder feeding rate of 30 g/min to prepare a cladding layer with more excellent performance.