VPS / LPPS

Versatile thermal spray process for the highest quality, reliability and durability to the exclusion of oxygen in low-pressure inert gas atmosphere.

The process is conducted in a vacuum chamber. The vacuum chamber is evacuated by a pump system before the process starts, to a pressure level of 0.08mbar. This ensures that residual oxygen or water vapor adhering to the chamber influence the high-purity gas atmosphere. Oxide free and dense layers on a pressure level of 60-300mbar may be applied under inert gas.

As with the atmospheric plasma spraying is also during vacuum plasma spraying generated with a DC voltage an arc between anode and cathode in a plasma torch. While the gas or a mixture of gas is flowing through the plasma torch, the arc ionized the plasma gas.

Dissociation, or subsequent ionization, produces a highly heated (20000 K), electrically conducting gas of positive ions and electrons.
In the generated plasma jet, which usually works with supersonic speed, powder (usual particle distribution: 5-120 microns) is injected. The high plasma temperature melts the spray powder.
The plasma jet pulls the powder particles and dashes them onto the substrate.
The gas molecules return after a short time back to a stable state. Thereby the plasma temperature drops after a short distance from the plasma torch again.
This extra energy is transferred to the powder particles. The nozzle contour is adapted to the reduced ambient pressure.

Process Basics:

Process characteristics

The plasma spray process produces enough energy to melt every material and thus offers a very high flexibility.
Plasma spray coatings can be very good controlled at their properties as thickness, porosity, roughness and hardness.

Typical Applications:        

Thermal Barriers:              turbine blades

Wear protection:                Turbine blades

Hi-tec coatings:                 Orthopedic implants, tungsten coatings