In-flight Particle Properties Research Articles

Influence of spray parameters on the particle in-flight properties and the properties of HVOF coating of WC-CoCr

Tungsten carbide-cobalt based spray coatings are widely used in industry for applications requiring abrasion, sliding, fretting and erosion resistance. High velocity oxy-fuel (HVOF) flame spraying has been used for producing high quality carbide coatings. In this study, a WC-CoCr powder was sprayed using a HVOF process. The spray parameters were varied to study their influence on the particle in-flight properties and the coating properties using on-line particle monitoring. The wear behavior of the coatings was evaluated both by rubber wheel tests and by pin-on-disk tests. It was found that the total gas flow rate and the powder feed rate could strongly influence the particle in-flight properties under the spray conditions in the study. By contrast, the spray distance had less influence than the above two parameters. In general, the higher the total gas flow rate, the lower the powder feed rate and the shorter the spray distance, the higher the particle velocity and temperature, and the denser and harder the coating. The rubber wheel tests showed that the total gas flow rate was of large significance for the wear resistance of the coatings.

Study on atmospheric plasma spraying of Al 2O 3 using on-line particle monitoring

In recent years, the interest in on-line diagnostic methods for thermal spraying has been increasing. The particle in-flight properties can be determined using such methods. One of the methods is on-line particle monitoring. In this investigation, study of atmospheric plasma spraying of Al 2O 3 was done using a DPV-2000 system (TECNAR, Canada). The influence of some spray parameters and the noise factor ‘wear of electrodes’ on the particle in-flight properties was investigated. It was found that the argon flow rate was the most influential factor for the particle velocity. The hydrogen flow rate influenced mainly the particle surface temperature. Increasing the electric current led to an increase in the particle velocity as well as in the particle surface temperature. The melting behaviour of the powder was significantly influenced by the particle velocity. The higher particle velocity resulted in a worse melting behaviour of the powder due to the shorter dwell time, leading to a lower deposition efficiency of the powder during spraying.

Influence of Plasma Spray Parameters on Formation and Morphology of ZrO2–8 wt% Y2O3 Deposits

Spray prints of thermal spray coatings were created on glass slides for air‐plasma‐sprayed 8‐wt%‐yttria‐partially‐stabilized zirconia (YSZ) deposits. The spray parameters such as carrier gas flow rate, standoff distance, and torch power were systematically changed to investigate the influence of these parameters on the YSZ deposit characteristics. The deposit properties such as deposition efficiency (DE), substrate coverage, deposit thickness, and roughness were measured. The deposits sprayed with a 3.5–4.0 L/min carrier gas flow rate at an 80 mm standoff distance exhibited higher values of DE within the range of studied process parameters. The DE increased as much as 25% by varying the carrier gas flow rate from 2.0 to 4.0 L/min. The deposits sprayed at a higher standoff distance and low torch power gave poor deposit characteristics. The deposit characteristics were compared with the in‐flight particle parameters and revealed that the deposit characteristics strongly depended on the in‐flight particle temperature. Using the in‐flight particle properties, the flattening ratio and the splat thickness were calculated. The average size of particles adhering to the substrate was found to drastically change with a change of process conditions, being much less than the average size of the starting powder.