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20ХН3А and 55СМФА steels increases their resistance to contact fatigue in 3 and

2.2 times in corrosive medium (water) and in 2 and 1.3 times in corrosive-abrasive

medium (water with quartz sand), respectively. Moreover, increasing the thickness

of the nanocrystalline surface layer increases their resistance to contact fatigue.

Scientific novelty of the obtained results.

For the first time, main parameters of crystallites with size in the range of 12

– 60 nm and a misorientation angle of more than 10 degrees, formed by

mechanical pulse treatment on pearlite carbon and low-alloyed steels, were

established. It was shown that the size of crystallites depended on technological

regimes of mechanical pulse treatment and the used technological environment.

For the first time, it was revealed that nanocrystalline structures, formed on

the 40X and 65Г steels using a mechano-pulse treatment method, retain a

nanostructured state under heating up to a temperature of 500 ° C. The regularities

of changing the size of crystallites in the surface layer in a nanostructural scale

range with an increase of heating temperature were established: the size of

crystallites was decreased at increasing temperature up to 300 °C and it was

increased at higher temperatures.

It was found that the hardened surface layer with nanocrystalline structure

on the 45 steel was characterized by lower hydrogen permeability (hydrogen

diffusion coefficient is in 1.3–4 times lower) and higher in 1.5–4.4 times efficiency

of hydrogen trapping in comparison with the untreated steel. Therefore, it serves as

a barrier for hydrogen penetration into the bulk material. It was shown that the

highest resistance of the steel to hydrogen embrittlement was provided by

nanostructurization of the steel surface using mechanical-pulse treatment with

multidirectional deformation in an oil technological medium.

It was established that coefficient of friction decreased significantly after the

surface mechanical-pulse treatment of steels. It was reduced in almost 4 times

under oil wear of the 45 steel in a friction pair with the ШХ15 steel.

Practical significance of the obtained results.

The method of mechano-pulse treatment of carbon and low alloyed