Extensión de durabilidad de pistones de bombas de fractura hidráulica mediante el empleo de tecnología de nitruración por plasma y PVD

Abstract

RESUMENLa técnica de estimulación hidráulica, consiste en "fracturar" la formación (roca reservorios) por intermedio de un fluido bombeado a alta presión y caudal. Esta operación se lleva a cabo mediante el empleo de bombas de fractura hidráulica. Los pistones de dichas bombas son los componentes mecánicos que realizan la admisión y compresión del fluido de fractura, mediante movimiento alternativo. Durante este ciclo, se produce el ingreso de finos de arenas al huelgo que media entre superficie del pistón y sellos, provocando el desgaste localizado del pistón.La tecnología de endurecimiento superficial empleada en la actualidad para la fabricación de estos componentes es el Thermal Spray, que presenta fallas propias de la técnica y de su forma de aplicación: inhomogeneidad química y estructural, porosidad y falta de adherencia al sustrato debido a discontinuidad metalúrgica entre metal base y recubrimiento.Este trabajo presenta los resultados obtenidos al reemplazar dicha técnica por la de endurecimiento superficial de Nitruración por Plasma propuesta por Y-TEC. La capa obtenida tiene una dureza superficial del orden de 1100 HV (Dureza Vickers), frente a los 550 HV alcanzables mediante la técnica reemplazada. El material base utilizado es un acero de Nitruración DIN 34CrAlNi7. El tratamiento propuesto se complementa con un segundo tratamiento de endurecimiento superficial mediante la técnica de PVD: Physical Vapor Deposition, que produce un recubrimiento monocapa de Al-Cr-N de 5 µm de espesor, con una dureza final de 2500 HV.El tratamiento de endurecimiento descripto, fue utilizado para fabricar una serie de pistones de bomba de fractura hidráulica, los que fueron ensayados en un piloto tecnológico de campo (PTC), complementado con ensayos de laboratorio estandarizados sobre probetas testigo del proceso de fabricación utilizado. La durabilidad medida de los pistones con la nueva tecnología implementada es 313% mayor a los de la tecnología Thermal Spray.Palabras clave: pistones, fractura hidráulica, desgaste, nitruración. ABSTRACTHydraulic stimulation technique consists of "fracturing" the formation (rock reservoirs) through pumping a fracturing fluid downhole. This operation is performed by using hydraulic fracturing pumps. The pistons of these pumps are mechanical components performing the intake and compressing fracture fluid by reciprocating action. During this alternative cycle, the entry of fine sand in the gap between piston surface and seals causes localized wear of the piston.Nowadays, commonly used hardening Technology for manufacturing these components is Thermal Spray, which has specific technical weaknesses: chemical and structural inhomogeneity, porosity and lack of adhesion to the substrate due to metallurgical discontinuity between metal base and coating. This paper presents the results obtained by replacing this technique for a new surface treatment using hardening by Plasma Nitriding. The layer obtained has a surface hardness of HV 1100 (Vickers hardness) versus HV 550 achievable with the techn...

Tribological behaviour of a multilayer CrN/DLC coating obtained using PVD-MS

“…In recent years, the oil and gas industry, among others, is demanding solutions regarding the durability of machine components in harsh environments [10], thus increasing the use of hard coatings and surface hardening processes to improve tribological properties and corrosion resistance. There are several kinds of coatings that can reduce the friction coefficient and the wear rate of materials, which will be useful to reduce operative costs, either fuel or electrical energy, but it will also reduce maintenance cost since its lower wear rate increases the life span of the components, thus fewer production stops will be needed to replace these elements.…”

Plasma nitriding of AISI 431 steel: surface hardness - hardness profile [Nitruración por plasma del acero AISI 431: dureza superficial – perfil de durezas]

“…Process temperatures vary from 350 °C to 580 ºC, with pressures from 0.1 to 1kPa, nitriding cycles range from ½ to 10 hours. Thanks to ionic bombardment, atoms of some pollutants are released from the surface of the material; the iron in the material reacts with nitrogen and forms iron nitrides (FeN), which causes the formation of a hard layer known as a "white layer", the chemical composition of this layer can vary depending on the chemical composition of nitrided steels ; the increase in the temperature of the piece and the ionic bombardment of nitrogen allows the diffusion of nitrogen atoms into the structure of the material, which forms nitrides with the alloying elements of steel such as, for example, chromium nitrides that protects the surface and could provide resistance to wear and corrosion; In addition, it increases the hardness in depth and resistance to fatigue (Cirimello et al, 2018). Moina et al (2002), evaluated the effect of ionic nitriding of martensitic stainless steels, concluding that nitriding treatments carried out for 20 h at 400 and 500ºC for AISI 410 martensitic steel produce a hardness greater than 1000 HV on the surface and profiles with abrupt interfaces due to rapid precipitation of CrN on the nitriding front.…”