High-velocity flame thermal spraying technology is widely used to apply coatings on industrial and aerospace parts, because a high flame speed yields coatings with high bonding force, high density, and low porosity. In this study, high-velocity oxygen gas fuel (HVOGF) and high-velocity oxygen liquid fuel (HVOLF) spraying processes were used to spray commercial powders of cobalt-based materials onto Inconel 718 substrates, and the flame characteristics of the two processes were observed using a real-time monitoring system during the spraying process. The metallographic and mechanical differences between the coatings produced by these two heat sources were then analyzed. The results showed that the velocity of particles produced with HVOLF was 1.23 times higher than that with HVOGF. Consequently, the melted powder produced with HVOLF led to a more compact metallographic structure. The resulting average values of microhardness and bonding strength were, respectively, 1.20 and 1.65 times higher with HVOLF than with HVOGF.