Laser cladding is a technology that uses high-energy-density lasers to quickly melt and solidify alloy powder on the surface of the metal substrate to form a cladding layer with good performance. Especially, martensitic stainless steel is widely used as a cladding material due to its high hardness and wear resistance. In this work, the martensitic stainless steel layers were fabricated on the C45 steel substrate by the laser cladding with different process parameters. The results show that holes in the cladding layer is unavoidable. The laser cladding process parameters have the important influence on the residual stress in the cladding layer. Under the action of residual stresses, the holes in the cladding layer will be the source of cracks, which will cause cracks in the cladding layer.

The potential of additive manufacturing has reached a point where the techniques are considered highly relevant for production purposes. In general, the manufacturing industry greets the new approach with enthusiasm, as it offers innovative designs and potentially reduced production costs. However, questions arise concerning the durability of additively manufactured components. This paper describes industrial trials with laser cladding and precipitation hardening heat treatment of thin-walled structures with the 17-4 PH stainless steel alloy. Due to the great relevance of the AM production methods for the aviation industry, the mechanical strength of the alloy given by the MMPDS document is used as a baseline. In order to improve the properties of the produced specimens, hot isostatic pressing was applied. The results show that a post processing treatment consisting of a HIP cycle and a conventional precipitation hardening, vastly improves the mechanical strength and elongation values of printed specimens, causing them to exceed the specified values.

Thermal spraying (APS and HVOF) of an agglomerated nanostructured powder, based on the composition of a commercial martensitic steel, is introduced. The nanostructure of the produced powder is examined by means of microscopy and X-ray diffraction. The influence of the two different processes on crucial properties such as porosity, microhardness, adhesion, and wear resistance is studied. High wear resistance is noted for both coatings. The HVOF coating, especially, showed better wear performance in comparison with the APS coating and the bulk martensitic steel. The superiority of the HVOF coating over the APS coating regarding the aforementioned properties is attributed to a higher retention of the nanostructure of the starting powder, higher peening and relatively low oxidation.

Cold Gas Spray allows to extend the range of steel coating formulations in comparison with other thermal spraying techniques because the material doesn’t melt during process. The absence of processes of fast solidification implies the absence of tensile stresses in the coating and makes possible to obtain thick coatings becoming a new alternative to welding cladding processes for the restoration of surfaces with corrosion pitting, notched areas or welded zones with bad appearance and for the repair of porous casting, contractions or losses of tolerance, by applying located coatings. 17-4 PH steel is one of the most widely used precipitation hardening grades in the business, offering high strength with corrosion resistance similar to S30400 in most environments. While soft and ductile in the solution annealed condition, it is capable of high properties with a single precipitation or aging treatment. Characterized by good corrosion resistance, high hardness, toughness and strength. Commonly used in both aircraft and gas turbines, nuclear reactor, paper mill, oil field, and chemical process components. A study has carried out in Thermal Spray Center for the production and optimization of thick coatings of 17-4 PH steel (S17400) through Cold Gas Spray technology onto carbon steel substrates. The study concentrates in the determination of influence of spray parameters on coating properties.

Thermal spraying of pure SiC is difficult due to decomposition issues at elevated temperatures. However, the development of suspension plasma spray opens a new path to investigate the deposition of this material since the liquid carrier can hinder this phenomenon. The present work investigates a new route for producing SiC submicron structured coating by suspension plasma spraying (SPS). Classical SiC manufacturing routes using suspension (i.e: spray drying, tape casting) are studied regarding their feasibility to be used on suspension plasma spraying. Aqueous-based suspensions containing 10 wt.% SiC powder (0.60 µm) along with sintering additives are dispersed and stabilized. Both suspensions are sprayed on martensitic stainless steel substrate (AISI 440C) to achieve finely structured and dense coatings. Digital image analysis, X-ray diffraction and scanning electron microscopy are utilized to characterize the coating microstructures. Their dependency on suspension characteristics and spray operation parameters are discussed with respect to the final coating performance.

This paper compares the corrosion resistance of electrolytic hard chrome plating and HVOF-sprayed WC-Co-Cr on two steel alloys used in landing gears. Test samples were evaluated by means of salt spray testing and electrochemical measurements. Post-test metallographic examinations were conducted to investigate the failure mode of the coatings. Test results are presented along with relevant findings and observations. Paper includes a German-language abstract.

Rotating bending fatigue tests have been conducted at room temperature in laboratory air using specimens of medium carbon steel (S45C), low alloy steel (SCM435) and titanium alloy (Ti-6AI-4V) with HVOF sprayed coating of a cermet (WC-12%Co) and S45C with WFS sprayed coating of a 13Cr steel (SUS420J2). Plane bending fatigue tests were also conducted at stress ratios, R, of -1, -0.5 and 0 for S45C with WC-12%Co coating. The fatigue strength and fracture mechanisms were studied. The fatigue strength evaluated by nominal stress was strongly influenced by substrate materials, R and the thickness of sprayed coatings. Detailed observation of crack initiation on the coating surface and fracture surface revealed that a crack was initiated in the coating and then cracks were initiated in the substrate due to the stress concentration of the crack in the coating. The fatigue strength of the sprayed materials was dominated by that of the sprayed coating. Therefore, the fatigue strength could be evaluated uniquely in terms of the true stress on the coating surface. The influence of compressive residual stress of the sprayed coatings on fatigue strength was discussed based on the fatigue mechanisms at different stress ratios.

The mechanical properties of plasma sprayed metals and alloys are important in most applications. It a posttreatment by forming of plasma deposited coatings is required, their response to compressive loading is decisive. This paper is concerned with the compressive behaviour of two high-alloy steels sprayed by a water stabilized plasma gun. Martensitic (13.2 % Cr) and austenitic (19.6 % Cr, 11.6 % Ni) steels were plasma sprayed onto plain steel substrates. Small cube-shaped test samples were cut out of thick coatings by an electrospark technique. Compressive load was applied along axes parallel and perpendicular to the substrate and coating surfaces. In addition, comparative samples of bulk steels produced by conventional metallurgy were tested. The compressive behaviour of the as-sprayed martensitic steel was anisotropic at room temperature, i.e. dependent on the orientation of the compression axis. As a result of compression, the splat shapes changed in a manner depending on the orientation of the compression axis. The room temperature compression tests showed that the yield stress of this steel was decreased and the anisotropy was reduced by annealing after plasma spraying. At room temperature, the anisotropy of the as-sprayed austenitic steel and the effect of annealing were less pronounced in comparison with the martensitic steel. Very low values of the yield stress were observed in both steels compressed at the annealing temperature. In spite of the presence of oxide films enveloping each splat, the coatings were prone to considerable plastic deformation, in particular if compressed along the axis perpendicular to the surface.