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Alternative TitleEffect of laser cladding process parameters on Nickel-based superalloy coating
Thesis Advisor虞钢
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline一般力学与力学基础
Keyword激光熔覆 镍基高温合金 工艺参数优化 温度-应力-应变场 硬度






Other Abstract

Superalloy is an important material for hot components in modern aerospace engines, spacecraft and rocket engines, and industrial gas turbine wheels, and it is also indispensable for nuclear reactors and chemical equipment. Nickel-based superalloy plays an important role in the whole field with higher high-temperature strength and structural stability. However, the shape of superalloy parts is complex, and the traditional material processing methods are difficult to achieve. Laser cladding technology provides an effective means to prepare geometrically complex parts. At the same time, it can reduce production costs by preparing high-performance coatings on inexpensive, easy-to-machine workpiece surfaces, and has been widely used in recent years. Because laser cladding is a multi-physics, multi-scale phenomenon process, the processing quality is depend on many factors. How to obtain cladding coating with high precision and mechanical properties is still a hot topic in the current research field. Due to the independence and relevance of factors, it is hard to consider them at the same time. As the most direct influencing factor, it is of great practical significance and engineering value to analyze the influence of process parameters on the quality of cladding.

In this paper, the laser spot shape, laser power, scanning speed and substrate temperature are selected as the object, and under different heat input conditions, the effect of temperature-stress-strain field evolution during cladding were studied. The effects of laser power, scanning speed and powder feeding rate on the morphology, solidification structure and microhardness of laser cladding Ni45 alloy powder cladding layer were studied by experiments. Based on the experimental results, the process parameters were optimized by PCA-TOPSIS method, and the influence of three process parameters on the size of the molten pool was analyzed. The main research contents and conclusions are as follows:

A three-dimensional model of synchronous powder feeding laser cladding was established to simulate the cladding process. The effects of spot shape, laser power, scanning speed and preheating temperature were studied. Through the analysis of the distribution of temperature, temperature gradient, cooling rate, stress and strain on the defined path, the influence of process parameters on the cladding process is obtained, which provides a theoretical basis for predicting the structure and properties of the coating.

Based on the law of numerical simulation, the experiment of laser cladding Ni45 alloy powder on 316L stainless steel substrate was designed. The effects of laser power, scanning speed and powder feeding rate on the quality of the cladding were studied by analyzing the morphology, microstructure and microhardness of the cladding layer. As an important factor that reflects the performance of the cladding layer. It is positively correlated with laser power and scanning speed, and negatively correlated with powder feeding rate. Controlling the dilution rate is the key to obtaining a high performance cladding layer.

The results of the experiment were comprehensively sorted by Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) that based on Principal Component Analysis (PCA). Considering the correlation between the factors, the optimized combination of process parameters was obtained: laser power 700W, scanning speed 3mm/s, and powder feeding rate 8.1g/min. In addition, the influence degree of three process parameters on the size of the cladding was analyzed, and the powder feeding rate, scanning speed and laser power were sequentially changed from large to small.

Call NumberMas2019-030
Document Type学位论文
Recommended Citation
GB/T 7714
赵尧. 激光熔覆工艺参数对镍基高温合金涂层的影响[D]. 北京. 中国科学院大学,2019.
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