니켈기 용사코팅의 미세구조 및 Tribology 특성에 관한 연구

Abstract

The thermal spray coatings are widely used in industry because they can give superior surface performance on substrate. In this work, the optimal process has been designed by L9(34) orthogonal array and analysis of variance(ANOVA) for Ni-based thermal spray coating. Ni-based thermal spray coatings were fabricated by flame spray process on steel substrate. Then, the hardness test, wear test and observation of microstructure of the coatings were performed. The results of hardness test and wear test were analyzed by ANOVA. From these results, the optimal combination of the flame spray parameters could be predicted. The calculated hardness and wear rate of the coatings by ANOVA were found to lie close to that of confirmation experimental result. Thus, it was considered that design of experiments design using orthogonal array and ANOVA was useful to determine optimal process of Ni-based thermal spray coating. The effects of process parameters on hardness and wear rate of Ni-based thermal spray coatings were investigated using design of experiments. First, the Ni-based thermal spray coatings were fabricated according to L9(34) orthogonal array. The hardness tests and the wear tests were performed on the Ni-based thermal spray coatings. The analysis of variance(ANOVA) for the hardness and wear rate were carried out. As a results, the acetylene gas flow and the powder feed rate were identified as main factors effected on the hardness and the oxygen gas flow and the acetylene gas flow were identified as main factors effected on the wear rate. The full factorial experiments design with different levels was applied for investigation of effect of these main factors. Process optimization for Ni-based thermal spray alloy coating has been performed using Taguchi method and analysis of variance(ANOVA). Ni-based thermal spray coatings were fabricated by flame spray process on steel substrate, and the hardness test and wear test were performed. Experiments were designed by Taguchi’s L9(34) orthogonal array and tests were conducted with different Oxygen gas flow, Acetylene gas flow, Powder feed rate and Spray distance. Multi response signal to noise ratio (MRSN) was calculated for the response variables and the optimum combination level of factors was obtained simultaneously using Taguchi’s parametric design. Thermal spray coatings developed by deposition of splats, it formed by impacting molten droplets on substrates during thermal spray process. In this study, the Ni-based coatings were fabricated by thermal spray process with two different process parameters, oxygen gas flow and acetylene gas flow, with three different levels of each parameters. The morphology splats and microstructure were observed by optical microscope. Hardness test were performed on the Ni-based coatings. It was confirmed that process parameters of thermal spray process have effect in morphology of splats. These effects also have important implications on the deposit microstructure and properties of Ni-based thermal spray coatings.