AISI H13 steel samples were additively manufactured using a laser powder bed fusion (LPBF) system. The effect of annealing tem-perature, quenching & tempering, and nitriding were determined. The microstructure and properties of the samples were investigated using optical microscopy, scanning electron microscopy, electron backscattered diffraction, electron probe micro-analysis, X-ray diffraction, roughness measurement, and a hardness tester. The results show that the as-built AISI H13 steel sample had a roughness on the surface and pores inside. The microstructure consisted of martensite and retained austenite. The average hardness was 460 HV, and the porosity was 0.086 %. The annealing process helped homogenize the microstructure, increase the density, and reduce the porosity and hardness of the LPBF-manufactured sample. The quenching process helped increase the hardness of the steel to the maximum of 787 HV, then the tempering process reduced the hardness to 572 HV. Heat treatment and nitriding processes tended to increase the martensite block size, reduce the retained austenitic content, and precipitate the V-Mo-rich carbide in the LPBF-manufactured AISI H13 steel. After nitriding was conducted, the nitriding case depth was 87 um, and the surface hardness increased up to higher than 1020 HV due to the formation of CrN and Fe3-4N.

Commercially pure titanium (Cp-Ti) is often used for biomedical implant devices but has low hardness and wear resistance; therefore, it is not suitable for use in the sliding parts or joints. Owing to their good wear resistance and biocompatibility, titanium nitride (TiN) coatings are used to improve these surface properties of Ti. This study aims to fabricate TiN on Cp-Ti by cathodic arc plasma evaporation and to investigate the effect of Cp-Ti substrate temperature on the properties of coated TiN thin films for biomedical applications. Coated TiN thin films were deposited on Cp-Ti at different substrate temperatures of 25, 100, 175, and 250°C. The surface morphology, roughness, phase composition, hardness, coating adhesion, and biocompatibility of the TiN coatings were investigated using a digital optical microscope, scanning electron microscope, X-ray diffractometer, hardness tester, and in vitro cell studies. Statistical differences were evaluated using analysis of variance (ANOVA) and Tukey's multiple comparison analysis, with statistical significance set at p < 0.05. Thin films with a primary TiN phase were formed on the surface of the Cp-Ti substrate regardless of substrate temperatures. There was no significant difference in surface hardness between the coated samples even though the sample coated at 100 and 175°C showed a slightly higher values, ranging from 193 to 199 HV. Interestingly, surface roughness and coating adhesion were significantly influenced by substrate temperature. The higher the substrate temperature, the greater the surface roughness, while the best adhesion, with the hardness of 176 HV, was obtained at substrate temperature of 25°C. In vitro cell study indicated that the baby hamster kidney cells on the coating surface have grown and proliferated better than those on the uncoated surface. The TiN thin film was successfully coated on Ti by cathodic arc plasma evaporation at different substrate temperatures, ranging from 25 to 250°C. The adhesion of the coating at low substrate temperature (25°C) was the best compared to other substrate temperatures of 100, 175, and 250°C. In vitro cell studies have demonstrated the biocompatibility of the coated TiN thin film.

This study investigates the effects of post-build heat treatments—such as annealing, quenching, and aging—on the microstructure and hardness of Laser Powder Bed Fusion (PBF-LB) Ti-6Al-4V. Specimens were subjected to annealing (950 °C, 1010 °C) or solution treatment/quenching (950 °C, 1010 °C), followed by aging (350–550 °C). Microstructural evolution was analyzed using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and Vickers hardness testing. Results showed that the as-built sample exhibited high hardness (365.2 HV_0.1) due to fine α′ martensite. Sub-β-transus annealing at 950 °C decomposed α′ into equilibrium α + 1.25% β (329 HV_0.1), while super-β-transus annealing at 1010 °C formed coarse lamellar structures of α + 1.5% β, yielding the lowest hardness (319 HV_0.1). Quenching from 1010 °C produced dominant α′ martensite with high hardness (371.6 HV_0.1). Notably, aging samples quenched from 950 °C increased hardness, peaking at 382.6 HV_0.1 at 450 °C due to precipitation, before decreasing to 364.4 HV_0.1 at 550 °C due to coarsening. These findings demonstrate that optimizing heat treatment temperatures is critical for controlling phase transformations and tailoring mechanical properties in additively manufactured Ti-6Al-4V components.

As-supplied SUS420 stainless steel was annealed at 880 °C for1 h and quenched (1040 °c, 30 min), followed by tempering at 530 °c for 1 h. The sample surface after tempering was polished with different roughness levels by mechanical grinding. Samples in the states of as-annealed, as-quenched and as-tempered samples as well as ground tempered ones with different surface roughness were gas nitrided with NH3 gas at 520 °c for 5 h. The microstructure and mechanical properties of SUS420 steel before and after the heat and surface treatments were investigated by optical microscopy, scanning electron microscopy, X-ray diffraction, and micro-hardness testing. The results show that if the natural oxide layer on the surface of the SUS420 samples was not removed, the nitriding process was very difficult or even imposible. The annealed steel gave the highest nitriding depth but low surface hardness. The samples after quenching and/or tempering had lower nitriding depth but higher hardness. The surface hardness of the as-supplied steel (333 HV) decreased with annealing (181 HV). After quenching, tempering, and gas nitriding, the values were 632, 560 and > 1000 HV, respectively. The samples after nitriding showed the appearance of fine CrN phase in the nitrided layer. The highest nitriding depth (125 pm) was obtained for the annealed samples, and subsequently decreased for the quenched samples and tempered samples. The lower the roughness of the sample, the higher is the hardness. The nitrided layer thickness tended to increase as the roughness decreased.

In this study, strain measurement can be analyzed in sub-10nm SiGe layer (~7 nm) grown on [100] Si substrate by chemical vapor deposition at the nanoscale level. The measurement technique is based on transmission electron microscopy (TEM), in which high-resolution transmission electron microscopy (HRTEM) image is combined with the image processing of geometric phase analysis (GPA) software. In this case, GPA analyzes the HRTEM images formed at the [011] zone axis to obtain information about strain maps along the [100] growth direction of the nanoscale SiGe region. The strain analyzed in the SiGe layer is within 1.6-2.9% with high precision and high spatial resolution.