Both as bulk material and coatings, cemented carbides currently occupy very well-established market niches and exhibit a promising future thanks to the development of compositions and manufacturing parameters. Direct comparisons of the properties of both are found only very rarely in the literature, very likely because the fields of application are complementary to each other but keep mostly separated. The current work is intended to evaluate similarities and differences in terms of microstructure and properties for two submicron WC-12 wt.%Co coatings obtained by High Velocity Air Fuel (HVAF) and Cold Gas Spray (CGS), together with a conventional sintered part. Microstructural features are discussed according to the inherent characteristics of each processing method. This covers a wide range in terms of the mechanical and thermal stresses acting on the material. While in CGS, the impacting particles do not melt, but experience extremely high plastic strain rates, the cobalt matrix is fully molten in the conventional sintering process, allowing time enough for diffusion processes. HVAF is to be placed in between, since the deposition process is characterized by a moderate heat input, leading to partial and/or full melting of cobalt, followed by rapid cooling. The microstructure and phases of the deposited coatings and bulk are characterized by using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Electron Backscattered Diffraction (EBSD) investigations enable local phase distribution of Co and WC in the samples. The hardness of the alloy processed by the three different routes is investigated as well. Additionally, electrochemical corrosion measurements in NaCl media are presented to evaluate the facility for electrolyte penetration and how the degradation of the material is affected by its inherent microstructure.

The aim of this work is to determine whether local disordering plays a role in the bonding of FeAl intermetallic coatings produced by cold spraying. XRD analysis of the powder and coatings revealed superlattice peaks, indicative of an ordered intermetallic structure. Nevertheless, locally disordered structures were detected in the deposits by TEM imaging. This may be related to a deformation induced order-to-disorder transformation due to the high strains involved in cold spraying, which is supported by comparing the magnetic properties of the deposits with those of HVOF sprayed coatings produced using disordered ball-milled feedstock.

This study investigates the impact behavior and consequences for coating formation in cold spraying of FeAl intermetallic compound powder. A range of spraying conditions was used to process single impacts in so-called wipe tests and for processing spray layers. In order to avoid brittle failure, high process gas temperatures and varied traverse speeds were used to account for thermal softening of spray particles and already adhering layers. Morphologies of as-impacted particles and partially removed single splats were subsequently investigated by SEM. The study of spray lines indicates that secondary impacts are only successful within an extremely narrow range of impact conditions. Within this narrow parameter regime, thicker and dense coatings are obtained. Hardness testing shows that the properties of the powders were retained.

Inconel alloy coatings have been obtained by means of Cold Gas Spray technology with a high efficiency. Alumina has been sprayed simultaneously achieving an homogeneous distribution along the deposit with a good cohesion between particles. Furthermore, the alumina particles were found to improve the spraying feasibility. A proper optimization of the spraying conditions has been carried out in order to obtain the lowest porosity as possible and good embedment of the alumina. Then, the mechanical properties as well as tribological and oxidation behavior have been characterized. Alumina behaves as reinforcement leading to an amelioration of the abrasive and friction performance. Regarding the oxidation and corrosion behavior, the coatings proved to withstand reasonably well up to 800°C and salt fog tests (5% NaCl solution at 35 °C) indicate durability up to 1000 h.

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.

Iron aluminides have been lately proposed as promising materials for wear applications. Many authors have focused their investigations on the friction behaviour of FeAl coatings emphasizing the role of this intermetallic as a new matrix to embed ceramic particles and replace for high temperature the extensively studied WC-Co cermet system. However, few works deal with the evaluation of the different tribological properties and their relationship with the coating microstructure. Thus, in the present study, the near stoichometric Fe40Al was successfully sprayed by means of HVOF using different spraying parameters and the tribological behaviour was assessed through solid particle erosion, abrasive and dry sliding tests. The wear mechanisms that took place in the produced coatings are discussed with regard to the obtained results. The friction coefficient versus sliding distance was obtained. In addition, isothermally treated samples in air were tested showing both lower friction coefficient and lower wear rate.

This study examines the oxidation performance of two different iron aluminide coatings obtained by means of High Velocity Oxygen Fuel spraying starting from the same feedstock powder but using propylene and hydrogen as fuels. The isothermal oxidation tests were carried out at 900°C for 4, 36 and 72 hours. After detailed observation a more rapid oxide scale growth is obtained for that coating obtained under hydrogen conditions. It leads to the assertion that propylene-coatings would perform better under high temperature environments.