Deposition and characterization of duplex treated coating system applied on hot work steel AISI H13 Deposición y caracterización de un sistema de recubrimiento duplex aplicado sobre acero para trabajo en caliente AISI H13

AISI H13 steel is widely used for extrusion moulds and other hot work tools fabrication, due to its high toughness, strength and hardness around 56 HRC (Rockwell C). However, this steel possesses a relatively low wear resistance, which reduces its life time under high loading conditions. The aim of this work was to enhance the wear resistance of the steel H13 using the following surface treatments: austenitizing + quenching + tempering (further called “tempering”), tempering and bath nitriding, tempering and coated with chromium nitride (CrN), tempering + bath nitriding + coated with CrN (further called “Duplex coating”). The properties of the treated samples were compared with each other in dependence of the made surface treatment. The coatings were deposited using the r.f. balanced magnetron sputtering deposition technique. The total thickness of the coatings was maintained at 5 μm, while the thickness of the nitrided zone was approximately 140 μm. The microstructure and the crystalline phase composition were investigated by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) technique, respectively. The hardness and the adhesion of the coatings were determined by micro indentation measurements and the Rockwell indentation test, respectively. The wear resistance of the coatings was evaluated using ball on disc tests. The duplex treated samples presented a hardness three order of magnitude higher and showed a wear rate six times smaller than those samples only tempered. El acero AISI H13 es ampliamente utilizado en la fabricación de moldes de extrusión y de otras herramientas para el conformado en caliente debido a su tenacidad, elevada resistencia mecánica, y dureza de aproximadamente 56 HRC (Rockwell C). Sin embargo, este acero posee una relativa baja resistencia al desgaste, que reduce su vida útil cuando es sometido a esfuerzos elevados. El propósito de este trabajo consistió en mejorar la resistencia al desgaste del acero H13 mediante los siguientes tratamientos superficiales: austenización + temple + revenido (denominado en adelante “revenido”), revenido y nitruración líquida, revenido y recubrimiento de nitruro de cromo (CrN), revenido + nitruración líquida + recubrimiento de CrN (denominado en adelante “recubrimiento Duplex”). Las propiedades de las muestras tratadas fueron comparadas en función del tipo de tratamiento superficial realizado. Todos los recubrimientos se depositaron por la pulverización catódica reactiva r.f. y asistida por un campo magnético balanceado. El espesor promedio de los recubrimientos fue de 5 micras, mientr