In this study Mn-Ni-Cr alloy was sprayed on AISI 321 stainless steel substrates using a thermal flame spray technique. For this purpose, the flame spraying method was used to create the coating of the aforementioned alloy as an interface layer in the brazing process. Regarding the importance of the absence of oxide phases in the coating, argon and nitrogen was used as a carrier gas for the brazing. The microstructure of coated samples was studied using scanning electron microscopy(SEM). It was observed that when used instead of air from argon and nitrogen as carrier gas, the amount of spreading lats was reduced and the porosity and prosity in the coating increased. Surface coatings were investigated by X-ray diffraction and it was observed that the use of protective gases reduced and eliminated some of the oxides. In this study, due to the high number of samples, the samples were first coated with air, under the brazing process, to obtain optimal parameters of temperature and time. The samples coated with argon and nitrogen gas at optimal temperature and time were subjected to brazing. Also, a foil with a similar composition of braze alloy was used to perform the brazing process. The process was performed by choosing a temperature of 1150 ° C as a constant temperature and changing the time of brazing process from 5 to 45 minutes to determine the optimum time. The results obtained from microstructural reviews and tensile strength tests indicate an optimum time of 45 minutes, then, at time of 45 minutes and the Temperature at 1110 ° C and 1130 ° C samples were brazed. Tensile strength test results indicate temperature of 1150° C for optimum temperature. Therefore, the samples coated with neutral gases as well as the desired foil were brazed at optimal temperature and time. Among of the samples coatted with the highest strength is 116 MPa and the minimum strength is 45 MPa. This is while the strength of the foil brazed sample is 405 MPa. The main factor in the strength of the brazing process is the manganese element, which can be completely dissolved in iron and form a strong metallurgical bond. Investigation of microstructure images and distribution of elements, indicating that the formation of solid solution and a brittle phase is not formed. On the other hand, the main reason is the strength difference between the samples brazed by coating and foil the surface discontinuities on the substrate that was created during the sand blasting process. Keywords:
