Influence of the intermediate layer forming method on the structure and properties of steel-aluminium system layered compositions
The technological features of manufacturing steel-aluminium system layered compositions with intermediate layer are considered. The influence of the intermediate layer forming method on interface structure, as well as the properties of layered steel-aluminum compositions is disclosed. For deposition of intermediate layer of pure aluminium of grades A5 GOST 7178 and AD1 GOST 4784 on low-carbon steel 20 GOST 1050 substrate the liquid-phase method of arc aluminizing using the Cold Metall Transfer technology, as well as the solid phase explosion welding process were used. It was shown that during the arc cladding process with a preliminary deposited intermediate aluminium layer Al-Si melt contacts not with pure steel. It contacts with the intermetallic layer of the Fe-Al system presented at the interface, which is accompanied by its partial dissolution. The dissolution degree depends on temperature and the existence time of the weld pool. With a continuous layer of the Fe-Al system intermetallic compounds formed during the deposition of an intermediate aluminum layer by arc aluminizing method using CMT technology the dissolution rate of the initial intermetallics is lower than the rate of new ternary Fe-Al-Si systems formation. It leads to an increasing from 8,2 to 18 μm in the average thickness of the intermetallics during the arc cladding of working coatings. The adhesion strength level of such coatings is 25 MPa. The discrete intermetallic layer of the Fe-Al system, formed during the deposition of an intermediate aluminum layer by explosion welding process, is completely destroyed upon contact with the Al-Si melt. As a result of it a new continuous layer of ternary Fe-Al-Si system intermetallic compounds is formed. The layer is characterized by a smaller thickness (10 μm versus 16 μm in the initial state). The specimens have adhesion strength level of 43 MPa. The achieved values of adhesion strength make it possible to recommend the produced steel-aluminum system layered compositions for using in friction units of modern technology.