Expanding the Technological Possibilities of Multilayer Micro-Plasma Powder Deposition Process by Optimizing the Quality and Composition of Process Gases

Abstract

Introduction. Mastering the micro-plasma powder deposition (MPWD) technology for refurbishing parts of nickel-based super alloy aircraft gas turbine engine (GTE) has been remaining a relevant task of the Ukrainian air craft industry for, at least, 15 last years.Problem Statement. MPWD or subsequent heat treatment of GTE parts made of nickel-based super alloy after long-term operating hours, with high γ'-phase content, might reveal increased cracking susceptibility. The search for ways to optimize the welding deposition technology has shown the necessity to scrutinize the positive technological effect of rational choice of the quality and content of process (shielding, plasma and transporting) gases.Purpose. To study the effect of process gas content on the heat source parameters, the conditions of the formation of deposited metal and its quality.Material and Methods. Comparative study of the micro-plasma (PPS04 plasmatron, UPNS-304M welding machine) and TIG (VSVU-315 power source) arc heat parameters depending on welding current and process gas has been conducted by the conventional flow calorimetry technology. Comparative estimation of the total work piece heat input parameters has been made based on the previously developed methodology with registering the welding current parameters based on m-DAQ14 analog-to-digital converter (ADC).Results. The comparative research during MPWD of sample parts has shown that the content and quality of process gases can significantly (up to 2.5 times) affect the amount of heat transferred into the work piece and, respectively, the possibility to provide the technological strength of “base-deposited metal” welded joint.Conclusions. The industrial MPWD process optimization by the criteria of work piece heat input parameters, technological strength of “base-deposited metal” welded joint and filler powder consumption,by means of increasing argon (plasma and transporting gas) quality by other gases impurities content and switch to 90% Ar + 10% Н2 argonhydrogen mixture shielding gas has been established to be promising and expedient way to solve the problem.