Search

The effect of the structural transformations during non-vacuum electron-beam cladding of amorphous boron powder on the hydroabrasive wear resistance of the surface layers of a chromium-nickel austenitic steel is studied. It is shown that the cladding yields a coating with densely arranged borides. An x-ray method is used to show that the modified layer consists virtually fully of Fe2 B iron borides. This structure raises the hydroabrasive strength of steel 12Kh18N9T by a factor of 1.5 – 2.

Structural changes developing in surface layers of plates from steel 20 in the process of explosive welding are studied with the help of light metallography and scanning and transmission electron microscopy. Mathematical simulation is used to compute the depth of the action of severe plastic deformation due to explosive welding of steel plates on the structure of their surface layers.

We consider structural changes occurring upon electron-beam hardening in air of rail steel M76. The microhardness of the hardened zone (thickness about 1.2 mm) is 800 – 900 HV. The short-term drawback using electron beam provides reduction of the microhardness to 400 – 700 HV. Electron-beam hardening also provides a 2-3 fold increase in the wear resistance of steel under the effect of abrasive particles. The data thus obtained make it possible to recommend the method of electron-beam treatment to strengthen the side edge of rail heads.

Special features of plastic deformation and fracture of excess cementite segregated under the conditions of high-temperature carbon supersaturation of steel are studied by the methods of light and scanning electron microscopy. It is shown that regularly oriented flakes of excess cementite with a lamellar structure are formed within the former austenite grains. The cementite flakes oriented along the, rolling plane fracture by a brittle mechanism forming numerous fragments. The behavior of free cementite under the conditions of cold rolling depends on the orientation of the flakes in the specimen. The mutual shift of the layers allows coarse cementite formations to deform under the action of compressive stresses without cracking.

1. Among the materials investigated the pitting formation process takes place most intensely in the M2 plasma coating. The resistance of the PG-SR4 coating to contact-fatigue failure is at the level of a similar characteristic of U8 steel with bainite structure after isothermal processing. 2. The controllable thermoplastic hardening of the U8 steel with subsequent treatment to bainite results in an increase in its fracture toughness, increases the resistance to contact-fatigue failure in comparison with normal isothermal processing. 3. For increasing the resistance to contact-fatigue of protective coatings, it is necessary to reduce their porosity, increase their cohesion strength and the strength of bonds with the base metal.