Progressive Surface, Grand Rapids, Mich., recently installed three 100HE plasma spray systems for the semiconductor industry. These systems are designed to spray very thin but dense yttrium oxide (Y2O3) coatings by the suspension plasma spray (SPS) technique. Each system includes the LiquiFeederHE suspension feed unit and the 100HE plasma torch. The as-sprayed Ra surface roughness for these coatings is typically in the 40 µ-inch (1 µm) range, which is ideal for these types of applications.
SPS requires more energy per deposited mass than conventional powder spraying because a liquid carrier must be vaporized before the plasma can interact with the coating material. The 100HE is well equipped to meet this increased energy requirement through the use of high enthalpy gas mixtures (Ar‐N2‐H2 or Ar‐N2‐He) and operating powers up to 105 kW. The small particle/droplet sizes within SPS increase the sensitivity of the feedstock materials, and thus the microstructure, to changes in the plasma flow. The ternary gas mixtures and high arc voltages (>200 V) of the 100HE generate an extremely stable plasma, allowing for consistent feedstock injection and heating.
Able to apply powders in axial, radial, or external injection modes, the 100HE produces superior plasma coatings applied at higher spray rates and significantly higher deposition efficiencies. It is capable of spraying coatings from 25 wt% solid suspensions and solutions (dissolved solid content) at flow rates of up to 90 ml/min with deposition efficiencies ranging from 50 to 80%.
