The processing of high-entropy alloys (HEAs) via laser metal deposition (LMD) is well known. However, it is still difficult to avoid chemical intermixing of the elements between the coating and the substrate. Therefore, the produced coatings do not have the same chemical composition as the HEA feedstock material. Single-layer CrFeCoNi and AlCrFeCoNi HEA coatings were deposited using high-speed laser metal deposition (HS-LMD). Elemental mapping confirmed a good agreement with the chemical composition of the powder feedstock material, and revealed that chemical intermixing was confined to the immediate substrate interface. The coatings are characterized by a homogeneous structure with good substrate bonding. The machining of these coatings via turning is possible. Subsequent diamond smoothing results in a strong decrease in the surface roughness. This study presents a complete manufacturing chain for the production of high-quality HS-LMD HEA coatings.

Cylinder linings of lightweight combustion engine blocks made from aluminium cast alloys are typically coated with thermally sprayed layers to enhance the chemical resistance. Finish machining of the cylinder linings is currently done by honing. A substitution of this process by machining with geometrically defined cutting edges would have significant advantages, especially concerning ecological aspects. For the investigations Fe17Cr2Ni0.2C iron based coatings applicated by atmospheric plasma spraying on substrates, prepared with a dovetail microstructure are machined by turning. In the experiments the feed is varied in the range of 0.025 mm to 0.15 mm. The tools used comprise CBN tips involving a rake angle of 0 degrees. Tool wear and machining forces are determined. The geometrical properties of the machined surfaces are detected by tactile measurements, 3D laser scanning microscopy and SEM. The residual stresses are characterised by XRD. An increase of the feed results in increasing components of the resultant machining force and higher values for Ra, Rz, Rpk, Rk and Rvk. Additionally, the amount of opened pores and pulled out coating material is reduced for high feeds. By increasing the feed the absolute values of the compressive principle stresses decrease. The increase of the knowledge in machining of thermally sprayed coatings by tools with defined cutting edges contributes to a substitution of the honing process and hence enables a more material and energy efficient production.

Austenitic high-manganese steels (HMnS) offer very high wear resistance under dynamic loading due to their high work hardening capacity. However, resistance to static abrasive loading is limited. Various approaches to increasing abrasion resistance are known from traditionally manufactured metallurgical components. These confirm the high potential for surface protection applications. In this work, the powder of the Hadfield HMnS X120Mn12 is prepared and processed by high-velocity oxy-fuel (HVOF) spraying and spark-plasma sintering (SPS). A good correlation was observed between the results of the HVOF and SPS specimen. Different surface conditions of the coatings and the sintered specimens were prepared by machining. Compared to the polished state, turning and diamond smoothing can increase the surface hardness from 220 HV to over 700 HV significantly. Regardless of the surface finish condition, similar good wear resistance can be demonstrated due to strong work hardening under sliding and reciprocating wear loading. In contrast, the finish machining process clearly influences abrasion resistance in the scratch test with the best results for the diamond smoothed condition. Especially against the background of current trends toward alternative coating systems, the presented results offer a promising approach for the development of HMnS in the field of coating technology.

Structural features of thermal spray coatings, e.g., porosity, can be beneficial as oil retention volumes in tribological systems in order to improve emergency running properties. While thermal spray coatings can already have a considerable degree of porosity depending on the coating conditions, the finish machining, e.g., by turning, has a significant influence on the final surface properties. Effects like near-surface deformation and subsequent closing of pores during the machining process should be prevented. In the present study, the influence of thermochemical surface hardening on the surface topography of wire arc sprayed 17Cr steel layers after finish turning was investigated. Successful surface hardening by gas nitriding was shown by light microscopic and phase analyses. The surface properties after the various treatment steps were characterized by the surface roughness parameters Ra and Rz, the valley void volume Vvv, and the Abbott curves. A rise of the valley void volume can be beneficial in tribological applications in which a suitable oil retention volume is required. Accordingly, a thermochemical treatment combined with an appropriate subsequent finishing process is suitable to significantly influence the surface properties of thermal spray steel coatings.

The aim of this study is to improve the fatigue limit of thermally sprayed EN 1.0032 steel substrates by combining turning, diamond smoothing, and temperature regulation during wire arc spraying of Ni-5wt%Al. In contrast to conventional shot peening, diamond smoothing induces defined and uniformly distributed compressive residual stresses, which will allow for an improved fatigue limit. In addition, the spraying process is observed using an infrared camera to study the influence of cooling between each layer application. The microstructure, phases, and residual stresses are examined by scanning electron microscopy (SEM) and X-ray diffraction. The uncoated and coated specimens are investigated regarding their quasi-static and high-cycle fatigue (HCF) behavior. After the HCF tests, the fracture surfaces are analyzed by stereomicroscopy and SEM. Diamond smoothing increases the fatigue limit in contrast to solely turned surfaces by 4.3 %. Furthermore, continuous thermal spraying of diamond smoothed surfaces reduces the fatigue limit. Cooling between the single-layer applications improves the fatigue limit but cannot compensate for all tensile residual stresses introduced by thermal spraying. The results of the present study show a first positive trend to increase the fatigue limit of thermally sprayed parts using diamond smoothing for pre-machining of a steel substrate and the temperature regulation during wire arc spraying. However, further studies are needed to improve the fatigue limit, as it seems that the compressive residual stresses induced by diamond smoothing with the parameters used are too small.

Magnetic properties are known to be crucial in the application of electrical steel and they are therefore covered by manifold studies. Other ferromagnetic materials are out of scope in this respect, even if the importance of magnetism of conventional steel is evident. Additionally, there is a contradiction regarding the major influence on magnetic properties. Machining, transport, and storage are possible influencing variables. In the experimental investigations, specimens consisting of the bearing steel 100Cr6 are machined by turning and partly by subsequent diamond smoothing. While machining using several cutting speeds and smoothing forces, the thermoelectrical voltage, current, and the components of the resultant force are recorded. The results show how the near-surface plastic deformations evolve throughout the machining process. Additionally, it was found that the magnetic properties and other properties of the surface layer are influenced in different ways depending on turning and diamond smoothing parameters. Correlations between in situ and ex situ measured values are shown. This study aims to solve the aforementioned question by quantification of machining impacts of cutting speed in turning and force in diamond smoothing and its dependence on transport and storage.