Effect of Surface Modification Heat Treatment on the Microstructure and Mechanical Properties of Self Fluxing Alloy(colmonoy 88) Manufactured by High Velocity Oxygen Fuel
Dong-Yeol Wi
Department of Materials Science and Engineering, Inha University,
Incheon 22212, Korea

Abstract

In this study, Ni-17W-15Cr-3B-4Si (colmonoy 88) powder and Co-32Cr-17W (stellite 1) powder were prepared by 1:0, 3:1, and 5:5 ratio to prepare a coating layer. Then, surface modification heat treatment was performed to control the microstructure and physical properties. The shape of the initial powder (colmonoy 88, stellite 1) was observed as spherical type, and its size was measured as colmonoy 88: 37.2 ㎛ and stellite 1: 26.9 ㎛. The colmonoy 88 powder consisted of γ-Ni phase and Cr5B3, W2B and Ni3Si phases. The addition of stellite 1 powder further confirmed the γ-Co peak. The thickness of the manufactured coating layers was found to be about 2 mm, and the second hard phase was additionally detected in all coating layers as the surface modification heat treatment was performed. Porosity gradually increased from 0.44% (1:0) to 3.89% (5:5) as the content of stellite 1 powder gradually increased. This phenomenon was observed due to the interfacial defects of unmelted particles due to the addition of stellite 1 powder. The surface porosity was denoted as 0.3% or less by performing the surface modification heat treatment. In the case of hardness characteristics, the addition of stellite 1 showed a gradual decrease from 625 HV (1:0) to 540.5 HV (5:5). As the surface modification heat treatment was performed, the hardness characteristics of all coating materials were improved. As a result of the wear test, it was confirmed that the wear resistances were improved by performing the surface modification heat treatment because the defects in the coating layer were controlled. Based on the above results, the wear surface of the coated layer was observed and the wear behavior of the as sprayed coating layer and the surface modified heat treated coating layer was investigated in connection with the microstructure.