Effect of mechanical and thermochemical tool steel substrate pre-treatment on diamond-like carbon (DLC) coating durability

Diamond-like carbon (DLC) coatings are becoming well established across many industrial sectors including aerospace, automotive, oil and gas, and cold-forming tools. While DLC coatings exhibit good mechanical properties and a low coefficient of friction, the coating–substrate systems may suffer from insufficient wear resistance. This paper describes the effect of mechanical and thermochemical tool steel substrate pre-treatment on DLC coating durability. We have investigated two tool steel substrates, Sverker 21 (AISI D2) and an advanced powder metallurgy alloyed steel Vanadis 8. Initially, the substrates were heat treated in a vacuum furnace and gas quenched resulting in hardness of 59 ± 1 and 64 ± 1 Hardness Rockwell C (HRC) respectively. Subsequently, the samples were subjected to mechanical turning and burnishing with 130 N and 160 N forces, using diamond composite tools with a ceramic bonding phase. Afterwards, a plasma-assisted vacuum nitriding process in a physical vapour deposition (PVD) coating chamber, as a pre-treatment for subsequent DLC coating deposition, was carried out. Coated samples were subjected to a series of ball-on-disc wear tests against Al2O3 and Si3N4 counterparts. X-ray diffraction, instrumented indentation and scanning electron microscopy were employed to examine the mechanical and chemical properties of the wear scars. Selected variable factors, including the type of steel, the burnishing force and the type of counterbody material, were analysed in order to correlate them with the durability of DLC coating deposited on a pre-treated steel substrate. The effect of sequential processes used as pre-treatment on DLC coating durability was demonstrated. The wear resistance was over 180 (Sverker 21 substrate) and 10 (Vanadis 8 substrate) times greater against the Al2O3 counterbody for samples subjected to the following treatment: turning + burnishing with 160 N force + vacuum nitriding + DLC coating, comparing with the sample after grinding. The results are discussed in light of improving the cold-forming tools' tribological performance

Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes

We review the different excitation processes in the interstellar mediumComment: Accepted in Chem. Re

Inclusions in bituminous salts from Kłodawa Salt Dome

Tak zwane sole bitumiczne są rodzajem skał solnych wykazującym znaczną zawartość węglowodorów nadającą im specyficzny kolor i zapach. W wysadzie kłodawskim występują w formie nagromadzeń o różnych wielkościach i kształtach. Najczęściej tworzą one nieregularne smugi, soczewki lub pasma o zróżnicowanych barwach zmieniających się od jasnożółtego po ciemnobrązowy. Badania petrologiczne tych utworów w płytkach grubych wykazały obecność bardzo różnorodnie wykształconych zespołów inkluzji fluidalnych. Zmienność ta dotyczy zarówno rozmiarów i kształtów inkluzji, jak i stosunku fazy gazowej do ciekłej oraz roztworów do zawartości węglowodorów. Pod tym względem wyróżnionych zostało siedem głównych typów zespołów inkluzji, pomiędzy którymi występują typy pośrednie. Występujące w poszczególnych zespołach inkluzji węglowodory także wykazują dużą różnorodność pod względem własności optycznych zarówno w świetle widzialnym, jak i ultrafioletowym.The so-called bituminous salts are a kind of salt rocks, which display considerable amounts of hydrocarbons giving them a specific colour and smell. In Kłodawa Salt Dome they occur as concentrations of various size and shape. Most often they form irregular streaks, lenses or bands of salts with different colours changing from light yellow to dark brown. The petrological investigations of such salts in thick plates showed a presence of very different fluid inclusion assemblages (FIA). They vary in size of inclusions, their shapes, the ratio of the gas to liquid phase and the ratio of solutions to hydrocarbons. In this respect, seven main types of FIA were distinguished including intermediate types, as well. Hydrocarbons occurring in singular FIA also show diversity in terms of optical properties in visible and ultraviolet light

Inclusions in anhydrite crystals from blue halite veins in the Kłodawa Salt Dome (Zechstein, Poland)

The occurrence of both the blue and violet halites is one of the most interesting phenomena in nature. Despite numerous laboratory and field works, their origin in natural evaporitic environments has not been satisfactorily explained. In the Kłodawa Salt Dome (Zechstein, Central Po land), blue or vio let halites occur relatively frequently. Their accumulations differ in size and intensity of colours. In this paper, petrological features of anhydrite crystals derived from one of the largest outcrops of the blue halite at the Kłodawa Salt Mine are presented. Anhydrite is one of solid inclusions encountered in blue-coloured halite crystals. Special attention was paid to fluid inclusions present in this anhydrite. The microthermometric measurements showed two directions of homogenisation, i.e., towards the liquid phase (LG→L, LL→L) ortowards the gas phase (LG→G). In the former case, the temperatures ranged from 174 to 513°C, whereas in the latter one, the values from 224 to 385°C were measured. The composition of inclusions is relatively variable. We can observe transparent and opaque daughter minerals as well as CO2 in the liquid phase accompanied by a variable amount of methane or hydrogen sulphide. These features of inclusions indicate that anhydrite crystals and, thus, blue halite were formed under the influence of hydrothermal conditions. Observations in the mine workings combined with petrological studies enable to conclude that blue colouration of halite crystals is controlled by three factors: a high temperature, reducing conditions and defects in halite lattice related to tectonic stress

Influence of tectonics on petrological characteristics of the anhydrite and anhydrite-halite intercalations in the Oldest Halite (Na1) (Zechstein, Upper Permian) of the Bądzów area (SW Poland)

The Oldest Halite (Na1) (Zechstein, Upper Permian) played a significant role in the development of geological structure of the Fore-Sudetic Monocline (SW Poland) because of its different rheological properties in comparison to the adjacent rocks. Intercalations of anhydrite and anhydrite-halite occurring within the Na1 show a lot of features of tectonically disturbed rocks. Macroscopic petrological observations revealed that anhydrite rocks represent four rock types with different structural and textural properties. On the microscopic scale, five types of crystals have been distinguished in all macroscopic types. They vary in size, shape and distribution of primary fluid inclusion assemblages. The anhydrite-halite rocks show two groups with slightly different petrological features that are apparently related to their tectonic deformation and recrystallisation processes. The main recorded directions of tectonic movements seem to be horizontal or sub-horizontal

Evidence of high-temperature rock salt transformations in areas of occurrence of borate minerals (Zechstein, Kłodawa salt dome, Poland)

Occurrences of borate minerals in the Zechstein salt-bearing deposits of the Kłodawa salt dome (central Poland), and the manner of their development, suggest that the minerals were formed at high temperatures, that considerably exceed the temperature estimated from the thermal gradient (~180°C). Research on rock salt and potassium-magnesium salts containing congolite and boracite, respectively, are consistent with high-temperature processes of transformations affecting the salt rocks in certain sections of the salt dome. The chemical composition of, and daughter minerals occurring in, primary fluid inclusions in halite, originating from the congolite zone, indicated a very high proportion of potassium and magnesium in the brines from which the halite crystallised. The thermal transformations observed in inclusions indicate a halite crystallisation temperature exceeding 420°C. Anhydrite crystals, co-occurring with borate minerals, represent unique features as to the distribution and composition of solid and fluid inclusions. These features indicate crystallisation or recrystallisation in conditions that differed considerably from those typical of the salt dome, with the involvement of solutions of changing chemical compositions. The crystals contain multiple solid inclusions of transparent and non-transparent minerals, among which we have focused on carnallite. The relationships of carnallite with liquid and gaseous phases indicate, as in the congolite zone, migration of very highly concentrated brines with respect to potassium and magnesium, or even transport of carnallite in the form of melt (liquid). Measurements of fluid inclusion homogenization temperatures, within the range from 197.8 to 473.8°C, supported a high-temperature origin for these minerals in hydrothermal conditions

Phase transitions in the borate minerals from the Kłodawa Salt Dome (Central Poland) as the indicators of the temperature processes in salt diapirs

The diapiric structures of the Polish Lowlands are tectonically deeply seated down to the autochthonous Zechstein strata at a depth of ca. 6 km. In the process of deep burial and halokinetic diapirism, the salt rocks were subjected to diagenetic and metamorphic transformations, with the temperature being an essential factor. Considering the thermal gradient, a temperature of up to ca. 200°C can be achieved in the salt dome within a depth range from several hundred metres to 6 km, which may lead to transformations of the majority of salt minerals. Phase transitions of two borate minerals – boracite and congolite from the Kłodawa salt dome – provide evidence for higher temperatures in the salt dome rocks. The authigenic euhedral crystals of those borate minerals display their external habitus in ambient temperature in the form of regular symmetry (F43c – pseudo-regular polyhedrons), whereas their internal structure is lower: orthorhombic (Pca21) for boracite and rhombohedral (R3C) for congolite. The heating and cooling of boracite and congolite crystals show reversible phase transition. At a temperature of ca. 270°C, boracite crystals change their symmetry: orthorhombic ↔ cubic. In the case of congolite three reversible phase transitions within a temperature range of 50–339°C can be observed: rhombohedral ↔ monoclinic ↔ orthorhombic ↔ cubic symmetry. Those phase transitions, confirmed experimentally in our study, clearly document at least local occurrences of temperatures exceeding 339°C in the Kłodawa salt dome

Neotectonic and recent movements revealed in the Bochnia salt mine

Badania nad neotektoniką i współczesnymi mchami tektonicznymi Karpat oraz przyległych struktur geologicznych trwają już od kilkudziesięciu lat. Rejon Bochni położony na granicy Karpat fliszowych i zapadliska przedkarpackiego zaliczony został w oparciu o badania geologiczne i geomorfologiczne do stref podnoszonych neotektonicznie. Złoże soli kamiennej Bochnia, eksploatowane od połowy XIII wieku, może stanowić bardzo dobry obiekt do obserwacji zjawisk geodynamicznych oraz wpływu neotektonicznych i współczesnych ruchów na wgłębną budową geologiczną. W niniejszej pracy autorzy podjęli próbę analizy występowania przejawów współczesnych i neotektonicznych ruchów w obrębie górotworu kopalni. Podstawowym celem było wyznaczenie takich wskaźników, które umożliwiałyby jednoznaczne stwierdzenie istnienia ruchów tektonicznych po ostatecznym uformowaniu się złoża oraz współczesnych, związanych wyłącznie z możliwymi dalszymi ruchami Karpat. Na podstawie przeprowadzonych w kopalni obserwacji za wskaźniki takie uznano: deformacje utworów wtórnych, żyły soli włóknistych, zaburzenia niektórych powierzchni nieciągłości i zróżnicowany stopień zaciskania wyrobisk górniczychExamination of neotectonics and recent tectonic movements of the Carpathian mountains and neighbouring geological structures have been carried out since a few decades. On the basis of geological and geomorphological examination Bochnia, the district situated at the border of the Carpathian flysch and the Carpathian Foredeep, has been ranked among neotectonically uplifted structures. The Bochnia salt deposit has been exploited since middle of the 13th century and may be a very convenient object for the study of geodynamic events and influence of neotectonic and recent movements on geological structure of the deposit. In the present paper the authors make an attempt at evaluation of recent and neotectonic movements within the rock mass. The main task was to distinguish such indicators which would make it possible to recognize the presence of tectonic movements originating after the last stage of salt deposit formation as well as those resulting from present-day activity of the Carpathians. Observations carried out in the Bochnia salt mine enable us to list the following indicators as: deformations of such secondary rocks as fibrous salt veins, disturbances of some surfaces of discontinuity and differentiated rate of convergence of the mine gallerie

Study of tectonic mesostructures in the "Bochnia" Salt Mine, South Poland

Złoże soli kamiennej Bochnia zlokalizowane jest przy brzegu Karpat, w strefie miocenu sfałdowanego, w elemencie tektonicznym zwanym antykliną bocheńską. Budowa wewnętrzna złoża jest skomplikowana na skutek intensywnych deformacji tektonicznych i różnych własności mechanicznych utworów budujących złoże. Efekty działania tych czynników można obserwować na ociosach wyrobisk kopalni bocheńskiej w postaci różnorodnych mezostruktur tektonicznych, takich jak: spękania, fałdy, lustra tektoniczne. Przeprowadzono pomiary i charakterystykę opisową mezostruktur tektonicznych w dostępnych rejonach kopalni bocheńskiej. Zwrócono także uwagę na wpływ własności mechanicznych iłowców i soli na rodzaj i charakter deformacji. Na podstawie tych danych dokonano próby określenia kierunków naprężeń tektonicznych, które działały na serię solną w rejonie Bochni podczas ich deformacji. Potwierdzono, że oś nacisku tektonicznego w rejonie Bochni przebiegała w kierunku S-N, ale występowało także odchylenie od głównego kierunku wzdłuż osi SW-NEThe Bochnia salt deposit is located in front of the Carpathian overthrust, in the area of folded Miocene strata. The tectonic element in which the deposit is situated is called the Bochnia anticline. The structure of the deposit is complicated due to intensive tectonic deformations and different mechanical properties of rocks which build the deposit. Effects of these processes can be observed in mine's workings, where many tectonic mesostructures, such as slickensides, folds with boudinage, tectonic breccias, and systems of fractures in claystone filled with fibrous halite occur. Tectonic mesostructures were measured in accessible mine's workings. The descriptive characteristic of mesostructures was also done. The impact of rocks' mechanical properties on the type and character of deformation was considered as well. On the basis of measurements, authors tried to characterize the direction of tectonic stresses which affected the salt series in the Bochnia area. Authors confirmed the S-N direction of tectonic compression but also indicated SW-NE deviation form the main directio

Evidence of high-temperature rock salt transformations in areas of occurrence of borate minerals (Zechstein, Kłodawa salt dome, Poland)

Occurrences of borate minerals in the Zechstein salt-bearing deposits of the Kłodawa salt dome (central Poland), and the manner of their development, suggest that the minerals were formed at high temperatures, that considerably exceed the temperature estimated from the thermal gradient (~180°C). Research on rock salt and potassium-magnesium salts containing congolite and boracite, respectively, are consistent with high-temperature processes of transformations affecting the salt rocks in certain sections of the salt dome. The chemical composition of, and daughter minerals occurring in, primary fluid inclusions in halite, originating from the congolite zone, indicated a very high proportion of potassium and magnesium in the brines from which the halite crystallised. The thermal transformations observed in inclusions indicate a halite crystallisation temperature exceeding 420°C. Anhydrite crystals, co-occurring with borate minerals, represent unique features as to the distribution and composition of solid and fluid inclusions. These features indicate crystallisation or recrystallisation in conditions that differed considerably from those typical of the salt dome, with the involvement of solutions of changing chemical compositions. The crystals contain multiple solid inclusions of transparent and non-transparent minerals, among which we have focused on carnallite. The relationships of carnallite with liquid and gaseous phases indicate, as in the congolite zone, migration of very highly concentrated brines with respect to potassium and magnesium, or even transport of carnallite in the form of melt (liquid). Measurements of fluid inclusion homogenization temperatures, within the range from 197.8 to 473.8°C, supported a high-temperature origin for these minerals in hydrothermal conditions