Geometrically complex parts are manufactured using wax casting. However, high-quality castings are not always ensured when using this method: defects often form on the product surface. Chemists from the Perm Polytechnic University suggested a technique that would avoid irregulari

Geometry Complex parts are manufactured using wax casting. However, high-quality castings are not always ensured when using this method: defects often form on the product surface. Chemists from the Perm Polytechnic University suggested a technique that would avoid irregularities in parts. This development has no analogue in the world.

The researchers published their results in the journal Glass & Ceramics (2022). The development is part of the world-class Perm REC ‘Responsible Use of Subsoil’ programme. The scientists used scientific equipment of the Science-Intensive Chemical Technology and Physical Chemistry Research Center of the Perm Polytechnic University.

"To make a complex-shaped metal part, an exact copy of it is first made using a special wax composition. The wax is poured into a collapsible mold under pressure. In order not to stick to the metal surface, the composition is pre-coated with release agent with waterproof properties. The model is then removed from the mold and treated with ethanol.

10-12 layers of ceramic suspension are applied to the wax, which is dried periodically and the resulting shell is calcined. When immersing the ceramic suspension for the first time, it is important to make sure that it covers the front layer of the mold without defects," says Nikolay Ulev, associate professor at the Department of Chemical Technology and candidate of Chemical Sciences at Perm Polytechnic University.

Measurement of wax plate wettability

Future important details The performance depends on the quality of the front layer of the mold, so the wax surface must be well wetted. To do this, use surfactants as well as chemical or physical methods. Recently, industrial companies most often use hydrocolloid compositions that are environmentally friendly and practically neutral. But their main disadvantage is that they do not always wet the wax with sufficient quality. Because of this, there are problems with the surface quality of ceramic molds and the bonding of the products.

Separating lubricants on the wax surface

"We conducted a series of experiments and found that the release agent layer remaining on the mold will prevent the wax from wetting. During the work, we used 10% sodium hydroxide solution to clean the The wax surface is treated without rinsing with water and ozone . The first method leads to a gradual change in the properties of the ceramic suspension, which is therefore not suitable for use. The most effective method is ozonation. exceeding the results given by standard methods," the researchers explain.

Chemists also determined that adding the high molecular weight substance alkyl benzene sulfonic acid to paraffin helped improve the quality of the parts. The scientists say the technology will be expected to be implemented in the metallurgical industry and mechanical engineering, especially when changing the material of wax models, which can lead to failure in ceramic mold manufacturing.