Laser cladding as an efficient production technology to realize bi-metal parts for plain bearings
Dr.-Ing. Hannes Freisse
Summary
An established material group for plain bearings are tin bronzes, which are used in various applications. Tin bronzes show an excellent tribological behavior against steel. However, tin bronzes have a low young modulus, which could lead to more elastically deformation during loading. To face this challenge, tin bronze can be applied on steel substrate, which offers a higher young modulus and thus higher stiffness. These coated steel parts are called bi-metal parts on which bronze acts as the functional tribological layer where it is needed, and the steel body offers the higher stiffness. Conventionally, the bronze is deposited onto steel by casting in a manual process with low resource efficiency. Laser cladding emerged as a promising alternative with high productivity, no need for masking and increased resource efficiency.
In this work, new insights are shown on how the heat input into the substrate material can be reduced by high-speed laser cladding (HSLC) – leading to less residual stress and no cracking. Since the absorptivity of infrared light is low for bronze, a shorter wavelength laser source is used for the deposition of bronze by HSLC. A higher process efficiency was observed. The hardness profile indicated a low heat input into the substrate. In metallographic cross-section, no intermetallic compounds or cracks were found. The results of the adhesion strength testing showed a strong bonding between substrate and bronze coating for plain bearings.
