Warm-particle peening assisted HVOF spraying: A new process to improve the coating performances

In order to improve the coating quality to a higher level, a method of warm-particle peening assisted thermal spraying was put forward. This work presents a study based on a warm-particle peening assisted high-velocity oxy-fuel (WPPA-HVOF) spray system, in which the spraying powder was injected from the port near the gun nozzle throat and the peening media was injected from the port outside the gun barrel exit. A type of FeBSiNb amorphous coating was prepared by the WPPA-HVOF process and compared with that of the traditional HVOF process. The in-flight particle velocity and temperature were tested using a high-speed thermal spray process monitoring system, which manifests that the velocity and temperature of the awaiting deposit powder are hardly affected by the addition of peening particles. Through characterization of the deposit by methods such as SEM, EDS, and FIB, it was found that the peening particle is rebounded after impacting on the substrate. As a result, there were no peening particles mingled in the deposited coating even when the feed rate was as high as 140 g/min. A by-product is that the coating structure becomes dense, e.g. the porosity can be as low as 0.7%. The WPPA-HVOF process results in a decrease in coating surface residual stress to compressive state. The properties such as microhardness, cohesive strength and wear resistance increase to varying degrees consequently. It is hypothesized that this is attributed to the large compressive residual stress because of warm-particle peening during the deposition process. [Display omitted] •A warm-particle peening assisted high-velocity oxy-fuel spray process was developed.•The WPPA-HVOF coating residual stress can be adjusted from tensile to compressive.•The peening particles are rebounded after impact and no one mingled in the deposit.