The Study of Brazing 422 Stainless Steels

• Main Authors: Chia-Lin Ou, 區家麟
• Other Authors: Ren-Kae Shiue
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/77229924678535252576

碩士 === 國立東華大學 === 材料科學與工程學系 === 90 === 422 stainless steels are featured with good corrosion resistance, oxidation resistance and moderate creep strength, so they can be applied in steam turbine blades. However, the carbon content of this alloy is high, and the 422 stainless steel contains many elements, such as Cr, Mo, V, W … etc., resulting in high hardenability. Consequently, this alloy is difficult to be welding or repair welding. Based on the requirement of the braze alloy with good corrosion resistance, oxidation resistance as well as moderate creep strength, both Nicrobraz LM and 130 nickel-base filler are used in infrared repair brazing as well as traditional brazing of 422 stainless steels. According to dynamic wetting angle observations, LM filler has the better wettability on the 422 stainless steel, and it can be brazed under lower temperatures. With aid of microstructural observations and chemical analyses, B in LM filler diffuses into the interface, and the filler matrix is primarily comprised of high Ni content phase. On the contrary, a few eutectic phases are left in the 130 filler matrix, even with a higher brazing temperature. Additionally, the Fe-Cr-B intermetallics is formed at the interface of the joint for both LM and 130 nickel-base filler. For LM filler, the residual intermetallics at the interface can be almost completely removed for long time annealing. Therefore, the LM nickel-base filler can be used in brazing 422 stainless steels at lower temperatures.