This study examines the effects of N 2 and He process gases and heat treatment on the microstructure and mechanical properties of 3D-printed pure copper produced using a low-pressure cold spray system. Microstructural analysis is performed through optical microscopy, while tensile tests are used to evaluate mechanical properties. Samples processed with N 2 demonstrate improved plastic deformation, leading to reduced porosity compared to those processed with He.

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.

The coefficient of thermal expansion (CTE) of a NiCoCrAlY coating was investigated in this work. The CTE was inferred from the measured length variations of coated prismatic symmetric specimens (i.e. having the coating on two opposite surfaces) at various temperature increments. The elongation of the specimen was evaluated from the relative positions of two markers, which was recorded during the test by a CCD video camera; analysis with subpixeling technique allowed high resolution in the dilatation measurements. Analytical relationships used to determine the coating's CTE were based on the simple multilayer beam model; the temperature dependent elastic moduli of the layers had been determined by four point bend test in a previous work. Coated specimens were employed having different substrate thicknesses in order to check the accuracy of measurements.

Spray and Fuse coatings are ideally suited to boiler environments. The fusing step gives to optimized coatings a uniform chemistry and microstructure, a metallurgical bonding, no through porosity, a low oxide content and no cracking. The relative simplicity of the traditional processing equipment is suited to on-site and automated application including coating repair. Although enjoying considerable success in traditional boilers, their advance into new applications appears restrained by the issue of substrate property modifications during fusing. This paper studies the modification in substrate boiler tube materials (microstructure and mechanical properties) associated with the coating of advanced NiCrBSi alloys. Charpy impact, tensile strength, yield strength, elongation and thermal expansion coefficient testing between 22°C and 450°C are measured. By optimal coating design to a specific substrate, the effect on mechanical property modifications by fusing could be dramatically reduced to allow new and reliable coatings systems to be demonstrated for advanced applications. The future for Spray and Fuse coatings in boilers is discussed.