A new low-cost chromium carbide-nickel chrome powder has been developed. Potential applications for these powders include hard-chrome replacement, boiler tubes and turbine engine components. The erosive and abrasive wear properties of the deposited coatings have been found comparable to commercially available nickel-chromium based carbide materials. A significant advantage of these powders is higher deposition efficiency and carbon retention when coatings are deposited using HVOF thermal spray equipment. Results indicate deposition efficiencies up to 50% higher than commercially available carbide powders in the market today. Higher deposition efficiency effectively reduces the application costs allowing these materials to be competitive in a wider range of applications. Powder characteristics and the application costs data are included in this paper. Also discussed are microstructure-property relationships of the various coatings. Data including abrasive slurry wear, hardness, high- and low-angle erosion and superfinished surface finish is reported. Comparisons have been made to commercially available chemical clad and blended CrC-NiCr powders.

Quasicrystals are materials whose structure cannot be understood within classic crystallographic methodology. Quasiperiodic structures have a long-range orientation order but lack transitional periodicity. This non-periodic structure gives quasicrystals a unique range of physical properties including: poor thermal conductivity; excellent crystallographic stability up to their melting point; can be thermally sprayed to display either wear resistant or abradable characteristics; possess excellent release properties (low coefficient of friction); and, they are non-work hardenable. This effort describes parametric conditions utilized to deposit coatings of identical parent metal chemistry but with vastly different end properties.

Exposed to particle erosion environments, metal-sprayed coatings are damaged by micro-machining and ploughing at low impact angles. The generation and propagation of subsurface lateral cracks at high impacting angles damage single-phase ceramic coatings. Therefore, multicomponent coatings deposited by high-energy processes have been widely used to provide wear protection in most of the applications. As commercial arc-sprayed coatings have been used to a limited extent in applications involving erosion and abrasion wear, developing attractive wear resistant arc-sprayed coatings has been found necessary. A cored wire formulation, referred to as Alpha-1800, has been developed to produce tailored arc-sprayed coatings that are tough enough to resist particle impacts at 90° and sufficiently hard to deflect eroding particles at low impact angles. Typical 1 mm-thick coatings composed of ductile and hard phases with Knoop hardness reaching 1800 kg/mm2 were easily produced by arc spraying the cored wire with air. Coatings were: 1) erosion tested at 25°C and higher temperatures at impact angles of 25° and 90° in a gas-blast erosion rig, 2) slurry erosion tested at impact angles of 25° and 90°, 3) abrasion wear tested using the ASTM G-65 test procedure. Results show that coatings produced with the new cored wire are at least 5 times more erosion resistant and 10 times more abrasion resistant than coatings produced by arc spraying commercial cored wires. The performance of the new arc-sprayed coating can be compared with that of high-energy WC-based coatings. Being thermally stable up to 850°C, arc-sprayed coatings produced with the new cored wire are attractive for applications in many industrial sectors up to high temperatures.

There is a continued need within the aerospace and space communities to increase the structural efficiency of launch vehicles in order to increase the payload and/or lower fuel usage. Many of these structures have critical stiffness demands because of deflection, buckling, or acoustic/vibration damping. Aluminum-beryllium (Al-Be) is a candidate material for many such structural components because it has a very high stiffness to weight ratio (second only to pure beryllium) and has superior formability and weldability as compared to beryllium. The strength to weight ratio of commercial Al-Be is superior to aluminum alloys (7050 and 6061-T6) that are currently used for aerospace and space applications. Plasma spray forming of Al-Be alloys is being investigated at Los Alamos National Laboratory for producing axial symmetric components for aerospace and space applications. Plasma spray forming of beryllium and beryllium alloys was investigated during the 1960's and 70's by Union Carbide Speedway Laboratories and the Atomic Weapons Establishment for producing axial symmetric launch vehicle components for defense related applications. Information is presented on the thermal and mechanical properties of plasma sprayed AlBeMet which is a commercial Al-Be alloy produced by Brush Wellman Inc.

Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite the use of the latest developments of thermal spraying, such as HVOF and plasma spraying, these coatings may in certain operation conditions show inadequate performance, e.g. due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding bulk materials. The main cause for a low bond strength in thermal sprayed coatings is the low process temperature, which results only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the chemical and structural inhomogeneity of the thermal sprayed coating material. In order to overcome the drawbacks of sprayed structures and to markedly improve the coating properties, laser remelting of sprayed coating was studied in the present work. The coating material was nickel based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The coating was prepared by high-velocity oxy-fuel spraying onto mild steel substrates. High power continuous wave Nd-YAG laser equipped with large beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed and after laser remelting were characterized by optical and electron microscopy. Laser remelting resulted in full homogenization of the sprayed structure. This strongly influenced positively the performance of the laser remelted coatings in adhesion, wet corrosion and high temperature oxidations test. The properties of the laser remelted coatings were compared directly with the properties of as-sprayed HVOF coatings, and with PTA overlay coatings and wrought Inconel 625.

The use of plasma spraying can be very beneficial in a rapid prototyping/manufacturing route for producing industrial metallic parts, e.g. tools and molds. Compared to the most recent and advanced laser-based or flame/arc spray-based methods, plasma spray basically shows a higher efficiency and process control in addition to a wider range of coating materials and better coating properties. This work deals with plasma spraying of AISI 316 stainless steel onto conventional MVA 200 acrylate resin as the second stage of a rapid prototyping route involving stereolithography plus plasma spray. This resulted in a 3 key issues : - Achieving a good coating/substrate adhesion, notwithstanding the preventing from previous grit blasting of the resin and poor physico-chemical bonding between the organic substrate and stainless steel ; - Good building-up of the sprayed particles up to a rather high thickness (i.e. of a few mm) through adequate plasma spray conditions, which limits the residual stress level; - Coating conforming closely to the substrate geometry, which precludes from surface damaging under spraying. The work showed that the process can meet all the previously-mentioned requirements combined with the achievement of high-quality coatings (i.e. with a low porosity in particular). A major part consisted in optimizing the plasma spray conditions using a CAPSATC ("Controlled Atmosphere/Temperature Plasma Spraying") unit. This included the development of an original thermal pre-treatment of the substrate (patented), namely "PINPRO", to promote coating/substrate adhesion. SEM, EDS, EPMA, FTIR, QIA (Quantitative Image Analysis), ... were particularly employed to study microstructures and interfaces. Phenomenological approaches to the involved adhesion mechanisms and coating build-up are discussed. For the latter, the first steps in the application of Lattice-Gas Modeling (LGM) of stainless steel layer build-up were made. LGM is a new and powerful simulation tool for the spray operator or user.

Cored wires show a high potential for production of protective coatings for combined corrosion and wear applications. Iron and nickel based grooved cored wires without and with different reinforcing carbide fillers have been sprayed by arc- and high velocity combustion wire (HVCW) spraying with a Praxair Type 216 gun. Depending on the wear mechanism coatings with a similar abrasive or oscillating wear resistance like HVOF WC/Co/Cr 86/10/4 have been produced. For effective protection against oscillating wear wires with a large diameter and therefore a high content of reinforcing carbide filler have to be applied. All nickel based coatings with chromium addition show an improved corrosion resistance compared to HVOF-sprayed WC/Co/Cr 86/10/4. For coatings from wires with NiCr 80/20 velum no effect of severe sulphurous corrosion in the DIN 50018 test is observed. HVCW-spraying is especially suitable, when only a low degree of interaction between velum and filler material is wanted as for cermet-like coatings. Conventional arc-spraying rather meets the demands of a high degree of interaction between velum and filler necessary for the production of pure metallic coatings like NiCrBSi. All manufactured coatings show good machinability.

Ni+Al, Ti+Al, NiCr+AI, and Cr+Al powders react exothermically in the heat zone of thermal spraying systems. Whether such reactions occur between aluminum and superalloy powders is the underlying question of this study. This paper describes composites of this nature and their sprayability to form adherent, metallurgically bonded deposits. Through parametric manipulation, coatings can be produced with a range of properties from dense to open (porous/abradable) structures. The paper also shows how seed particles can be clad with aluminum and sprayed to predictable property limits.

Alumina matrix composites reinforced with metal thin wire (Inconel-600) were successfully fabricated by plasma spray forming. The atmospheric plasma sprayed matrix layers and wire layers arranged by filament-winding technique were piled up alternately. Though the matrix and the wire were partially bonded only on the side which sprayed particles came flying to, a solid structure was obtained by this technique. Spraying in one direction perpendicular to the substrate made peculiar V-shape pores around the wires, but tilting the torch was effective to reduce the pores. The flexural strength of composite did not increase in spite of some crack deflections on the fracture surface. Owing to the wire pullout, however, the composite exhibited a remarkably higher apparent fracture energy than that of monolithic alumina ceramics.

This paper compares two types of hydroxyapatite (HA) composite coatings, HA/Ti-6Al-4V and HA/Y-ZrO2. The powders used in the study were prepared using a slurry process then deposited by plasma spraying. The resulting coatings were characterized based on their microstructure, mechanical properties, and biocompatibility. Both composite coatings performed better than pure HA coatings in tensile adhesion and indentation tests. Testing also revealed that the HA/Y-ZrO2 coatings had favorable strength and fracture toughness and that the HA/Ti-6Al-4V coatings had good affinity to living tissue and sufficient mechanical strength.

Methodology to evaluate the adhesive strength between the MCrAlY alloy coating film and the Ni-base superalloy substrate was studied and proposed. By employing the double cantilever beam specimens which were taken from the CoNiCrAlY alloy coated Ni-base superalloy, the fatigue crack propagation tests along the interface were carried out. Through the work particular attention was given to the threshold level to the fatigue crack propagation along the interface as a measure to represent the adhesive strength, based on fracture mechanics approach. The effects of temperature, the surface finishing of the substrate and the long term thermal aging on the adhesive strength were also investigated.

A technology and a specialized equipment complex based on supersonic arc spraying gun, where a supersonic stream of combustion products of hydrocarbon-gas (HC-gas) with air is used as an atomizing gas, have been developed. Durable and safe work of coated parts functioning under conditions of intensive loading is determined (except general requirement to coatings: wear resistance, hardness) to a large extent by the fatigue strength, porosity and stability of the properties of coatings. New possibilities for satisfying all the requirement to coatings on parts type are opened up by a high speed spraying of wire. This is provided at the expanse of raising the kinetic energy of particles under spray, increase of their concentration in metal stream, lowering of the spread of parameters in the vicinity of a substrate. This, in its turn, determines the increase of adhesive and cohesive strength of coating, the decrease of oxidation, the improvement of stability and reproducibility of its properties. The results of the investigations of the influence of the variable parameters of the process on the listed above properties of coatings are presented. This technology and equipment complex is appreciated for repair of wearied motor component and deposition of corrosion protective coatings.

It has been observed that VC-WC-Co hardmetals have a better wear resistance than conventional WC-Co hardmetals. This work represents a first attempt to add VC to thermal spray powders in order to determine whether this would increase the wear resistance of HVOF hardmetal coatings. Standard WC-Co and WC-CoCr thermal spray powders were compared to two experimental VC-WC-Co powders in terms of size distribution, morphology and phase composition. Coatings were produced from the powders using the TAFA JP-5000 High Pressure High Velocity Oxy-Fuel (HP/HVOF) process. The microstructure, phase composition, hardness, dry solid particle erosion and three body abrasion of the coatings were compared. It was found that due to the non-homogeneous dispersion of VC particles in the powders, the experimental coatings were not optimised. Nevertheless they showed some advantage over the conventional coatings, particularly in low angle erosion tests. This result is regarded as promising, and it is believed that a homogeneous dispersion of VC particles in the coatings would result in a significant increase in wear resistance. In order to test this, the manufacture of improved powders and optimised coating microstructures would be necessary as a next step.