PTA – COATING AND IMPREGNATION

There is no limit to the number of layers and the PTA method can therefore be used both for repairs (many layers for larger damages) and for surface coating as part of new manufacturing.

 

The big advantage of PTA compared to conventional welding methods (MIG/ MAG, TIG, MMA, etc.) is that the energy can be controlled much better.

 

This means that less base material needs to be melted to get a good weld, which results in significantly less mixing, i.e. cleaner welds.

 

Although the temperature may be higher in the melt, the total heat into the material is significantly lower, which results in a considerable reduction in deformation.

 

In addition, PTA is a continuous process, which means that the heating is evenly distributed, thereby further reducing movement in the workpiece.

 

Thanks to the high performance of PTA, materials that are otherwise difficult to weld can be coated with good results. It is therefore a logical consequence that the method is most often used for hard facing. Typical applications are valves, nozzles and similar.

 

The recent trend in renovations, however, is that details and materials that were previously applied with thermal spraying are increasingly being replaced by PTA.

 

This involves building up materials with ordinary carbon steel or stainless/acid-resistant steel that is placed on proprietary material.

 

A typical repair is a bearing seat or a sealing position that has failed. In this type of repair, we can advantageously renovate the detail with a nobler material to locally increase performance, for example, a sealing position on a carbon steel shaft is coated with stainless material to not only obtain the correct geometry but also better withstand the environment.

 

Surftech's latest technological development is plasma impregnation. The method is based on a ceramic material (e.g. Tungsten Carbide) being applied to the surface followed by melting using PTA as a heat source.

 

The ceramic material is then mixed with the molten metal and forms a MMC (Metal Matrix Composite) on the surface. This MMC is not a layer that can crack and come off, but is integrated into the part itself.

 

Using PTA as a heat source results in very small shape changes and a relatively smooth surface. Parts can therefore be manufactured according to the original drawing and, after plasma impregnation of non-toleranced wear surfaces, still have the correct geometry.

 

Typical applications are pulleys, scrapers, knives and the like that are exposed to heavy wear.