The paper describes the microstructure of welded joints produced by the plasma+MAG (Metal Active Gas) method of S700MC high yield strength steel (700 MPa). Welded joints of thermomechanical steel have been made with different values of heat input. The results of metallographic research of welded joints, microstructure of the weld and heat affected zone, hardness distribution and impact toughness are presented. The heat affected zone consists of two sub-zones with different grain size and lowered hardness. The tensile test show that strength of welded joints was slightly reduced and the bending test revealed no crack formation in the weld. The impact toughness of measured welded samples with V-notch in HAZ (heat affected zone) reached high values that are higher comparing to samples with notch placed in the weld area. The investigation results show that the use of plasma concentrated heat source together with MAG welding arc does not significantly change the structure and deteriorate properties of welded S700MC thermomechanically treated high strength steel. The hybrid plasma+MAG welding method has a potential to become a beneficial alternative to other welding processes due to its high efficiency, reduced amount of weld metal content or limited requirements for a preparation of edges of welded joints.

The article presents selected properties of a titanium metallization coating deposited on aluminum nitride (AlN) ceramics surface by means of the friction surfacing method. Its mechanism is based on the formation of a joint between the surface of an AlN ceramics substrate and a thin Ti coating, involving a kinetic energy of friction, which is directly converted into heat and delivered in a precisely defined quantity to the resulting joint. The largest effects on the final properties of the obtained coating include the high affinity of titanium for oxygen and nitrogen and a relatively high temperature for the deposition process. The titanium metallization coating was characterized in terms of surface stereometric structure, thickness, surface morphology, metallographic microstructural properties, and phase structure. The titanium coating has a thickness ranging from 3 to 7 μm. The phase structure of the coating surface (XPS investigated) is dominated by TiNxOy with the presence of TiOx, TiN, metallic Ti, and AlN. The phase structure deeper below the surface (XRD investigated) is dominated by metallic Ti with additional AlN particles originating from the ceramic substrate due to friction by titanium tools.

The paper presents the microstructural investigation of a friction-welded joint made of 316L stainless steel with an ultrafine-grained structure obtained by hydrostatic extrusion (HE). Such a plastically deformed material is characterized by a metastable state of energy equilibrium, increasing, among others, its sensitivity to high temperatures. This feature makes it difficult to weld ultra-fine-grained metals without losing their high mechanical properties. The use of high-speed friction welding and a friction time of <1 s reduced the scale of the weakening of the friction joint in relation to result obtained in conventional rotary friction welding. The study of changes in the microstructure of individual zones of the friction joint was carried out on an optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and electron backscattered diffraction (EBSD) analysis system. The correlation between the microstructure and hardness of the friction joint is also presented. The heat released during the high-speed friction welding initiated the process of dynamic recrystallization (DRX) of single grains in the heat-affected zone (HAZ). The additional occurrence of strong plastic deformations (in HAZ) during flash formation and internal friction (in the friction weld and high-temperature HAZ) contributed to the formation of a highly deformed microstructure with numerous sub-grains. The zones with a microstructure other than the base material were characterized by lower hardness. Due to the complexity of the microstructure and its multifactorial impact on the properties of the friction-welded joint, strength should be the criterion for assessing the properties of the joint.

The article presents the results of research on the structural evolution of the composite Fe-Al-based coating deposited by arc spray with initial low participation of in situ intermetallic phases. The arc spraying process was carried out by simultaneously melting two different electrode wires, aluminum and low alloy steel (98.6 wt.% of Fe). The aim of the research was to reach protective coatings with a composite structure consisting of a significant participation of FexAly as intermetallic phases reinforcement. Initially, synthesis of intermetallic phases took place in situ during the spraying process. In the next step, participation of FexAly fraction was increased through the annealing process, with three temperature values, 700 °C, 800 °C, and 900 °C. Phase structure evolution of the Fe-Al arc-sprayed coating, stimulated by annealing, has been described by means of SEM images taken with a QBSD backscattered electron detector and by XRD and conversion electron Mössbauer spectroscopy (CEMS) investigations. Microhardness distribution of the investigated annealed coatings has been presented.

The aim of this paper is to describe the selected mechanical properties and microstructure of butt welded joints obtained by the hybrid Plasma+MAG method of S700 MC steel (high strength Re=700 MPa). The results of metallographic research of welded joints, microstructure of the weld and heat affected zone, hardness distribution and impact toughness are presented. The tensile test shown that strength of welded joints was slightly reduced and the bending test revealed no crack formation in the weld. The impact toughness of measured welded samples with V-notch in HAZ (heat affected zone) reached high values that are higher comparing to samples with notch placed in the weld area. The investigation results show that the use of hybrid plasma + MAG welding arc does not significantly change the structure and deteriorate properties of welded S700MC thermomechanically treated high strength steel.

The article discusses microplasma arc applications in welding, surfacing and remelting processes, describes the effect of microplasma arc and its burning conditions as well as presents the properties and the application range of plasma welding. In addition, the article presents examples of microplasma welded joints of thin elements and discusses the application of microplasma arc in surfacing and remelting as well as indicates advantageous features of plasma arc and its application potential as an alternative to other welding power sources.

StreszczenieCelem niniejszej pracy jest zbadanie wpływu energii liniowej na właściwości złączy spawanych wykonanych metodą hybrydową Plazma+MAG ze stali S700 MC (o wysokiej granicy plastyczności Re = 700 MPa). W ramach badań wykonane zostały spawane złącza próbne blach ze stali obrabianej termomechanicznie dla różnych wartości m.in. energii liniowej spawania. W celu zweryfikowania jakości oraz właściwości otrzymanych złączy, przeprowadzono badania niszczące, pomiary twardości oraz próby właściwości mechanicznych złączy.Słowa kluczowe: spawanie hybrydowe Plazma+MAG; stal o wysokiej wytrzymałości; S700 MC; stal termomechaniczna; energia liniowa spawania; badania niszczące AbstractThe purpose of this paper is to investigate the influence of heat input on the properties of welded joints produced by the Plasma+MAG method of S700 MC (high strength R e = 700 MPa). Welded joints of thermomechanical steel have been made with different values of heat input. Due to the verification of the quality and properties of the obtained joints, destructive tests, hardness measurements and mechanical properties of joints were performed.Keywords: Plasma+MAG hybrid welding; high strength steel; thermomechanical steel; heat input; destructive testing Wstęp Do budowy konstrukcji spawanych coraz częściej stosowane są nowoczesne materiały konstrukcyjne o podwyż-szonej wytrzymałości, które łączy się również nowymi wysokowydajnymi hybrydowymi metodami spawania. W pracy została wykorzystana nowoczesna metoda hybrydowego spawania Plazma+MAG (scharakteryzowana w pracach [6,7,9]) charakteryzująca się wysoką koncentracją ciepła w miejscu łączonych elementów, dzięki czemu możliwe jest wykonanie pełnowartościowych złączy o stosunkowo niedużej szerokości spoiny i dużej wysokości. W celu zbadania wpływu wartości energii liniowej na własności mechaniczne złączy doczołowych (stali S700 MC) zostały one poddane badaniom niszczącym. Praca przedstawia wyniki oraz analizę przeprowadzonych badań metalograficznych (makro-i mikroskopowych), pomiarów twardości oraz badań właściwości mechanicznych tj. statycznej próby rozciąga-nia i zginania oraz próby udarności.Beata Skowrońska, Jacek Szulc, Tomasz Chmielewski, Dariusz Golański Stal obrabiana termomechanicznie o wysokiej granicy plastycznościObróbka cieplno-plastyczna jest najbardziej efektywnym sposobem poprawy właściwości mechanicznych, ponieważ uzyskuje się jednoczesne zwiększenie granicy plastyczności, polepszenie ciągliwości i spawalności przy równoczesnym stosowaniu w stali relatywnie małej ilości dodatków stopowych. Najkorzystniejszymi mechanizmami umocnienia stali wysokowytrzymałych są rozdrobnienie ziarna, utwardzenie wydzieleniowe i utwardzenie dyslokacyjne [1÷4]. W celu obniżenia kosztów produkcji tego rodzaju stali przy zachowaniu ich wysokich właściwości wytrzymałościowych bez znacznego pogorszenia spawalności, zaczęto wytwarzać stale konstrukcyjne z mikrododatkami oraz stosować procesy dodatkowo zwiększające wytrzymałość. Przykładem tak otrzymywanych materiałów są stale walcowane termomechaniczni...

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