NiCrSiBC alloy: microstructure and hardness of coatings processed by arc and laser

• Published in: Welding International 2017-01, Vol.31 (1), p.1-8
• Main Authors: da Silva, Leandro J., D'Oliveira, Ana Sofia C. M.
• Format: Article
• Language: English
• Subjects: Alloys; Austenitic stainless steels; Coatings; Cooling rate; Deposition; Dilution; Hardfacing; Hardness; laser cladding; Lasers; Microstructure; Parameters; plasma transferred arc; processing; Protective coatings; Strength; Welding
• ISSN: 0950-7116; 1754-2138
• DOI: 10.1080/09507116.2016.1218608

The processing technique is decisive for the characteristics of a coating. This is because the heat supply, which depends on the technique and on the parameters, has an influence on the dilution and the solidification rate. In alloys with low metallurgical complexity, the effect of processing with deposition techniques that give a higher cooling rate may be translated into refining of the microstructure. A more refined microstructure is expected to result in higher mechanical strength of the coating. However, in the deposition of alloys that are more complex metallurgically this does not always occur, because the high cooling rate may suppress formation/precipitation of phases responsible for strength. The influence of processing on the microstructure and hardness of coatings of alloy Colmonoy-6 ® was assessed in this study. The alloy was processed by plasma transferred arc and high-power diode laser on plates of AISI 304 with two levels of dilution. In both cases, good-quality, defect-free coatings were obtained. Increase in Fe content (dilution) and different cooling rates result from processing with different parameters and techniques. This leads to significant changes in microstructure and hardness of the coatings, associated with the distribution, morphology and chemical composition of the carbides and particularly of the borides.