Modification of piston surfaces by compressed plasma flow

Abstract

Surface of the casted pieces made of aluminium piston alloys was treated by a plasma jet produced by the magnetoplasma compressor, with an aim to improve their exploitation properties. Fast piston surface heating and melting, physical and chemical changes within the surface layer and the melted layer recrystallization in the fast cooling conditions are the basic characteristics of the interaction between the plasma from the magnetoplasma compressor and piston alloys. The major changes are conducted in the surface layer inducing hardness increment and piston resistance. Micro hardness of plasma treated surface is 750 to 883 HV_0.2, in comparison with 90 to 130 HV_0.2 in initial stage. The X-ray structure analysis of samples in cast state before and after plasma treatment shows existence of modified zones in hardened layer with phase transformations. In plasma flow treated surface at least two new phases are registered, with redistribution of already existing phases. These intermetallic phases contributed to treated surface hardness increasing. These observations show that quasi-stationary compressed plasma flow treatment of sample surface influences remarkably modification and improvement of surface properties.