The subject of the invention is a method for modification of top layers of working surfaces of machine parts, which is used for the treatment of top layers of working surfaces of machine parts, and especially for placement of coatings of micro- and nanometric solid greases in the unevenness of the surfaces of extrusion punches and on sliding guides of machine tools.

Modification of top layer consists of feeding of foreign material particles in the hammer strike zone, which alongside with the plastic microdeformation of the treated layer causes an adhesive connection of these particles with the native material of the treated item. The feeding of foreign material particles is performed by: spreading of a paste, dipping in a suspension, rubbing, feeding from a container etc.

Currently, for the modification of the surface with foreign material particles, a surface treatment with dynamic methods is used, such as: shot blasting, ball burnishing and tumbling.

The dynamic methods are based on probabilistic distribution of imprints of the operational tool in the form of balls, shot etc., on the treated surface, which does not guarantee a uniform micro-deformation of the surface and the distribution of deformations. This treatment also requires feeding of a much higher amount of foreign material particles than the amount required for placement over the treated surface. As a result, these processes do not guarantee an even spread of foreign particles over the treated surface. The method of hammering is not used for the surface modification with foreign particles. This results from the principle of a mechanical (a cam driving a spring) or pneumatic (pneumatic actuators) drive which causes a relatively large deformation of the top layer and as a result large coarseness of the surface on the level Ra=20-10 μηα of and the use of additional finishing treatment (grinding), and also from too low energy supplied to the hammer in current mechanical and pneumatic drives, which does not enable the exerting of a sufficient unit pressure in order to create an adhesive bond.

The essence of the invention, which is a method for the modification of top layers of working surfaces of machine parts by hammering and spreading of foreign material, consists of the treated surface, in the zone of the ram, which is a hammer with a ball-shaped working area, connected with a piezoelectric actuator, which is driven by a high frequency voltage generator with a frequency changeable within the range of 10 Hz to 1000 Hz and a relative movement of the hammer in relation to the treated material along the acting line within the range of 0.05 to 5.0 mm, is covered with a layer of foreign material, which becomes connected by adhesion with the top layer of the modified surface under the pressure exerted by hammer.

Through the use of the solution presented in the invention it is possible to perform controlled modification of the top layer of working surfaces of machine parts which improve their mechanical, structural and tribological properties, and increase their smoothness and precision, which as a result extends the operational period of these parts and advantageously influences the natural environment.

In particular, it enables a control over the dynamics of the strikes of the piezoelectric actuator, which enables the control of the amount of energy of the hammer which produces microdeformations of the top layer, guaranteeing the hardening which does not exceed the limiting values of plastic deformation of crystallites. The essential feature of this solution is a uniform distribution of foreign particles on the treated surface which result from the synchronised movement of the treated item (feed) and the working tool powered by a PE actuator controlled by the frequency generator (strike frequency, amount of provided energy). This synchronisation enables a permanent distance between the imprints and the depth of the imprint. This solution guarantees a uniform distribution of imprints over a unit of surface of the product, which translates into a uniform placement of foreign objects over the treated surface.

Additionally, a uniform microdeformation of the surface cause compressive stresses in the top layer, and thus it improves mechanical properties (including fatigue strength, hardness), tribiological properties (by increasing the abrasion resistance) and geometric properties (improving the smoothness and precision of construction).

Additionally, during the hammering process it is possible to control the value of local deformation over the treated surface, and thus the ability to control the mechanical properties which vary over different fragments of the treated surface.

The proposed solution is relatively easy to be used in numeric control systems.

An important advantage of the proposed solution is that the amount of used foreign material particles necessary to modify the top layer is only slightly larger than the amount necessary to coat the treated surface. This is very significant in case of expensive materials or nanomaterials, which are manufactured in minute amounts.

The subject of the invention was shown in an example presentation, illustrated by a diagram figure, presenting the unit for the implementation of the method of the invention.

The piezoelectric actuator 1 is mounted at a set distance to the treated surface. To the end of the piezoelectric actuator 1 a hammer 2 is attached - a tool with a ball-shaped end acting on the treated surface. The drive of the piezoelectric actuator 1 is provided by a high frequency voltage generator which ensures its reciprocal movement with a set frequency and the input function curve characteristic. These parameters allow the control of the energy of the hammer strike to the treated surface. The treated object 3 moves in a direction perpendicular to the direction of movement of the hammer 2. As a result of the strike of the hammer 2 the deformation of the top layer of the treated material 3 occurs. At the same time the foreign material particles 4, used to modify the top layer 5 are subjected to a high local pressure created between the end of the hammer 2 and the top layer of the treated material 3, which causes the deformation of foreign material particles and adhesive bonding of the particles with the top layer surface 5.

Modification of the top layer 5 of working machine parts by hammering and spreading of foreign material, using the method in the invention, is realised by covering the top layer 5 of the treated element 3 with a layer of foreign material 4 which, under the pressure of the hammer 2 bonds adhesively with the top layer 5 of the modified surface. The hammer 2 with a ball-shaped working area is driven by a high frequency voltage generator 1 with a frequency changeable within the range of 10 Hz to 1000 Hz, whereas the hammer 2 moves in relation to the treated material along the acting line within the range of 0.05 to 5.0 mm,

Initially compressed piezoelectric material, subjected to electric current, lengthens in proportion to the amount of the applied voltage.

The speed of lengthening depends directly on the speed of voltage increase. An acceleration in an amount of thousands of gees can thus be obtained. This is a feature which was used in dynamic applications, such as used in the invention.

The frequency and strength of hits of the ram attached to the piezoelectric element depends on the current voltage, intensity and frequency and on the inertia of the mechanical system of the ram. The control of these parameters enables the adaptation of the character of the strikes to the requirements of the process.