Process-oriented modeling and simulation of unsteady modulated gas flows in plasma powder cladding to influence layer properties

本研究项目的目的是开发一种方法来识别和表征时变非平稳调制过程气流对等离子体熔覆过程中熔体反应的振荡和电流的影响。期望通过硬颗粒的良好分布和微观组织的细化可以实现力学性能的改善。本文将介绍两种合金作为等离子弧的硬质材料粉末。这两种合金是钨钴合金和钨钴合金以及碳化钨。焊接熔池凝固过程会改变钴钴钴合金粉末，使枝晶生长中断，从而获得晶粒更细的镀层。添加碳化钨的钨晶石的目标是通过搅拌焊池来抵消碳化钨的重力偏析，从而实现整个焊缝中碳化钨的均匀分布。这项调查的结果应该使人们有可能对PTA堆焊过程中产生的物理效应的瞬态过程气流有一个基本的了解，并从这些知识中开发经济用途。然后，这些知识可以通过改变这些覆盖层的微观结构和宏观结构来增强该工艺的磨损性能，并且进一步用于扩展当前的应用范围。

The objective of this research project is to develop an approach to identify and characterize the effects of time-varying non-stationary modulated process gas streams on the melt reaction during plasma cladding with regards to oscillation and current. It is expected that an improvement in the mechanical properties can be achieved with a favorable distribution of hard particles and through refinement of the microstructure. Two alloys will be introduced as hard material powder to the plasma arc during this investigation. The two alloys are a stellite cobalt alloy and a stellite alloy alongside tungsten carbides. The cobalt stellite powder will be altered by the weld pool solidification process such that dendritic growth is interrupted, in order to obtain a more fine-grained deposit. The goal for the stellite with the added tungsten carbides is to achieve an even distribution of tungsten carbides throughout the weld by agitating the weld pool to counteract gravity segregation of the tungsten carbides. The results of this investigation should make it possible to have a basic understanding of transient process gas streams in a PTA hardfacing process with regards to the resulting physical effects and to develop economic uses from this knowledge. This knowledge can then be used to enhance the wear properties of this process by changing the microstructure and macrostructures of these overlays, and furthermore be used to expand upon the current application boundaries.