THE EFFECTS OF BORON MINERALS ON THE MICROSTRUCTURE AND ABRASION RESISTANCE OF BABBITT METAL (Sn–Sb–Cu) USED AS COATING MATERIALS IN HYDROELECTRIC POWER PLANTS Yahya Tasgin Mechanical Engineering Department, Faculty of Engineering, Munzur University, 62000 Tunceli, Italy Copyright Ó 2019 American Foundry Society https://doi.org/10.1007/s40962-019-00359-4 Abstract In this study, the microstructure of a new alloy is examined which is created by adding boron oxide (B 2 O 3 ), boric acid (H 3 BO 3 ) and kolamanit (Ca 2 B 6 O 11 Á5H 2 O) in certain pro- portions to the white metals (Sn–Sb–Cu) used in the carrier bearing dies of vertical Francis turbines in hydroelectric power plants. The Babbitt materials were coated with electric arc spray coating method before. Also it is exam- ined that whether the coating material produced as a new alloy is appropriate for applying to die surface. Utility of the new white metal material in carrier bearing dies in hydroelectric power plants has been investigated based on the metallographic structure and wear of the new alloy. While some of the boron elements added to the Babbitt metal have positive results in terms of metallographic and abrasion values, some of the boron elements have negative effects. Keywords: Babbitt metals, EAS coating method, boron, wear, microstructure Introduction Research and development have become very important for the advancement of science and technology and the development of new tin-based materials. 1,2 So far, many materials have been tested as bearing components. In 1839, the Sn–Sb–Cu alloy was patented by Babbitt for this pur- pose. The Babbitt alloy Sn–Sb–Cu (white metals) has been indispensable for sliding bearings as a good coating material in steels. 3,4 Sn–Sb–Cu alloys are widely used as the Babbitt metals in truss bearings. The microstructure of these alloys consists of a soft solid solution matrix and two intermetallic compounds (CuSn, SbSn) which are harder than the matrix (Sn). This particular microstructure char- acterizes these alloys as carrier materials. 5,6 Babbitt metals are tin- or lead-based alloys that have excellent embedding and compatibility properties. Although high in cost, tin Babbitt is often used in its preference for leading Babbitt due to its excellent corrosion resistance, easy binding and less propensity to segregation. 3,7,8 Tin-based Babbitt usu- ally contains antimony and copper. 9 They have an adequate hardness number that gives them excellent load-bearing capability. They exhibit good emergency behavior when there is low friction resistance, low abrasion, good wear properties and not enough lubrication. It is easily ‘‘get wet’’ and keeps the oil film; also it is resistant to corrosion, easily poured and adhered and maintains good mechanical prop- erties at high temperatures. Furthermore, the amounts of antimony and copper cannot be increased, because the high antimony concentrations result in multiple agglutinations of the matrix and Sb–Sn crystals, and the copper forms a rigid interlayer that does not have sufficient toughness and leads to binding defects. Therefore, it has proven to be appropriate to limit the antimony to 12% and copper to 6%. Ishihara and Tamura 10 have examined the effect of anti- mony amount on slip resistance of white metal. The results showed that the shear abrasion resistance is not affected by the amount of antimony in the range of 5–18% by weight; however, the resistance decreases in the higher amount of antimony. Babbitt alloys generally consist of a soft matrix and rein- forcement phase. The alloy consists of a solid solution of antimony and copper in tin. In order to prevent abrasion resistance in the friction zones and to prevent heat extraction, a high pressure oil film layer is applied to the area to minimize the impact of the surface. 11,12 Babbitt alloys are generally not produced by pouring, because of their low recrystallization feature, they are strengthened by giving a cold shape. As a result, the rate of solidification International Journal of Metalcasting