Welding and Thermal Spray Processes for Maintenance of Hydraulic Turbine Runners: Case Studies

Abstract

Hydraulic runners are susceptible to failures by cracks or wear by erosion, corrosion, or cavitation. The modern runners are fabricated in carbon steel and martensitic stainless steel. Arc welding processes normally do the repair of eroded areas, or cracked parts. Each material or type of repair needs specific criteria, procedures, and precautions to guarantee their success and prevent future issues, like the recurrence of the cracks or reduction of the useful life of the runner by modifications of the original material. Wear-resistant coatings are applied by welding or by thermal spray processes, considering this last one has no metallurgical interaction with the material of the runner, keeping the original properties of the material. For several years the companies Copel GeT, Lactec, UTFPR, and UFPR collaborate on the study of different techniques, methods, and processes to repair hydraulic runners, this work aims to present a short compilation, and examples of some results obtained applied on real runners.

A Review of Advances in Cold Spray Additive Manufacturing

“…Other processes are presented in the literature but are not capable of producing complex geometries, such as Gas Tungsten Arc Welding (GTAW) [52][53][54], Gas Metal Arc Welding (GMAW) or Wire Arc Additive Manufacturing (WAAM) [55][56][57][58], Plasma Arc Welding (PAW) [57,[59][60][61], Friction Stir Energy Manufacturing (FSAM) [62,63], and Ultrasonic Additive Manufacturing (UAM) [64,65]. Examples of AM by welding processes that demand post-machining are repairing long fatigue cracks in hydro powerplant runners [66] or repairing eroded gas turbine blades [67].…”

Review on erosion phenomenon, maintenance, and financial calculation of lifetime as an asset for Pelton turbines

“…This uses lower temperatures to avoid changes in the structure of the base material. The use of subsequent heat treatments is always predominant to recover the mechanical properties exposed to temperature [52,53]. The recuperation process of a Pelton turbine has many steps, beginning with the erosion inspection, and ending with static balancing, transportation, and proper storage.…”

Avaliação do Desempenho no Ambiente de uma Caldeira de Revestimento Metálico de Liga à Base de Ferro Obtido por Aspersão Térmica a Arco Elétrico

“…Entre os vários métodos de proteção por uso de revestimento, a Aspersão Térmica (ASP) de um material adequado sobre uma superfície pode prolongar a vida útil da peça, mantendo suas propriedades mecânicas originais, enquanto protege contra o desgaste e a corrosão [7][8][9][10][11][12][13][14][15]. Comparativamente, o processo de ASP por arco elétrico é uma solução relativamente de baixo custo, rápida e simples de ser executada, podendo ser realizada em campo [16,17]. Seus benefícios refletem nos custos do processo, de forma que a substituição da peça revestida ocorrerá em um intervalo de tempo maior, e ainda, para uma aplicação que necessita que suas superfícies resistam ao atrito gerado por outras superfícies ou partículas, será possível a utilização de um material de menor custo com a aplicação de um revestimento altamente resistente a abrasão [7,13,18].…”