The aim of this work was to investigate the microstructure and mechanical properties of samples produced by direct metal laser sintering (DMLS) with varied laser beam speed before and after heat treatment. Optical analysis of as-built samples revealed microstructure built of martensite needles and columnar grains, growing epitaxially towards the built direction. External and internal pores, un-melted or semi-melted powder particles and inclusions in the examined samples were also observed. The strength and Young’s modulus of the DMLS samples before heat treatment was higher than for cast and forged samples; however, the elongation at break for vertical and horizontal orientation was lower than required for biomedical implants. After heat treatment, the hardness of the samples decreased, which is associated with the disappearance of boundary effect and martensite decomposition to lamellar mixture of α and β, and the anisotropic behaviour of the material also disappears. Ultimate tensile strength (UTS) and yield strength(YS) also decreased, while elongation increased. Tensile properties were sensitive to the build orientation, which indicates that DMLS generates anisotropy of material as a result of layered production and elongated β prior grains. It was noticed that inappropriate selection of parameters did not allow properties corresponding to the standards to be obtained due to the high porosity and defects of the microstructure caused by insufficient energy density.

The aim of the study was to clearly determine whether selected modern medical materials and three dimensional printing allow for satisfactory viability of human osteoblasts, which is important from the point of view of the subsequent osseointegration process. Moreover, as implants are produced with various topography, the influence of surface roughness on viability of bone cells was evaluated. To conduct the research, primary human osteoblasts (PromoCell) were used. Cells were seeded on samples of glass-reinforced polyetheretherketone (30% of the filling), Ti6Al4V manufactured with the use of selective laser melting technology and forged Ti6Al4V with appropriately prepared variable surface roughness. To assess the viability of the tested cells the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide was used. Results showed that all evaluated materials do not exhibit cytotoxic properties. Moreover, on their basis it can be concluded that there is a certain surface topography (designated i.a. as roughness equal to approx. Ra = 0.30 µm), which ensures the highest possible viability of human osteoblasts. On the basis of the received data, it can also be concluded that modern glass-reinforced polyetheretherketone or Ti6Al4V produced by rapid prototyping method allow to manufacture implants that should be effectively used in clinical conditions.

The purpose of this paper was to determine the influence of selected parameters of Direct Metal Laser Sintering and various heat treatment temperatures on the mechanical properties of Ti6Al4V samples oriented vertically (V, ZX) and horizontally (H, XZ). The performed micro-CT scans of as-build samples revealed that the change in laser energy density significantly influences the change in porosity of the material, which the parameters (130–210 W; 300–1300 mm/s), from 9.31% (130 W, 1300 mm/s) to 0.16% (190 W, 500 mm/s) are given. The mechanical properties, ultimate tensile strength (UTS, Rm) and yield strength (YS, Re) of the DMLS as-build samples, were higher than the ASTM F 1472 standard suggestion (UTS = 1100.13 ± 126.17 MPa, YS = 1065.46 ± 127.91 MPa), and simultaneously, the elongation at break was lower than required for biomedical implants (A = 4.23 ± 1.24%). The low ductility and high UTS were caused by a specific microstructure made of α’ martensite and columnar prior β grains. X-Ray Diffraction (XRD) analysis revealed that heat treatment at 850 °C for 2 h caused the change of the microstructure intothe α + β combination, affecting the change of strength parameters—a reduction of UTS and YS with the simultaneous increase in elongation (A). Thus, properties similar to those indicated by the standard were obtained (UTS = 908.63 ± 119.49 MPa, YS = 795.9 ± 159.32 MPa, A = 8.72 ± 2.51%), while the porosity remained almost unchanged. Moreover, the heat treatment at 850 °C resulted in the disappearance of anisotropic material properties caused by the layered structure (UTSZX = 908.36 ± 122.79 MPa, UTSXZ = 908.97 ± 118.198 MPa, YSZX = 807.83 ± 124.05 MPa, YSXZ = 810.56 ± 124.05 MPa, AZX = 8.75 ± 2.65%, and AXZ = 8.68 ± 2.41%).

In recent years, scientists have defined two main paths for orthopedic implant fabrication: searching for new materials with properties closest to natural bone in order to reduce the stress-shielding effect or creating individually adapted geometry of the implant with the use and Rapid Prototyping methods. Therefore, materials such as PEEK GRF30 and Ti6Al4V selective laser melting (SLM) are of interest. They are defined as materials suitable for implants, however, the knowledge of their bioactivity, a feature which is one of the most desirable properties of biomaterials, is still insufficient. Using Simulated Body Fluid and Hank’s Balanced Salt Solution, the bioactivity of PEEK GRF30 and Ti6Al4V SLM was assessed, as well as commercial Ti6Al4V as a reference material. Ten cylindrical samples of each material were prepared and immersed in solutions per period from 2 to 28 days at 37 °C. Optical analysis of the changes on the examined surfaces suggested that right after 2-day crystals with different morphologies were formed on each material. Further analysis of the chemical composition of the altered surfaces confirmed the formation of a calcium phosphate layer on them, however, the Ca/P ratio was slightly different from 1.67. On the basis of the obtained results, it can be concluded that both PEEK GRF30 and Ti6Al4V SLM are characterized by appropriate—comparable to Ti6Al4V—bioactivity.

A total hip replacement is a procedure that requires removal of the affected joint lesions and replacing it with artificial elements. Nevertheless, like any invasive surgery, it is associated with the risk of complications, including joint infection, fracture of the bone during and after surgery, scarring and limitation of motion of the hip, and loosening of the prosthesis. In this work we present and describe the results of its investigations. In order to determine the mechanism of failure, a broken stem components were analyzed by means of macroscopic and microscopic observations and hardness measurements. The hardness, microstructure and chemical composition of the broken part of the hip stem were analyzed. Microscopic examination revealed numerous defects in material. Among them are pores and emptiness, located on the outskirts of the tested samples and a plurality of micro-cracking, debonding and delamination of the material due to the overloading of a fatigue character. There were no changes caused by intergranular corrosion or pitting, which may indicate for an even distribution of the major alloying components such as chromium and nickel. Observations of the material by using scanning electron microscopy (SEM), clearly proved that the destruction was caused by material fatigue. The investigation showed that the crack had originated due to a high stress concentration on the lateral corner section of the stem. Large surface of the fatigue crack zone area indicated for small stresses and small crack propagation velocities. There was a clear correlation between the grain size of the steel hardness. The results of hardness test revealed a significant increase hardness of stem in relation to the normative values. In addition, the measured average grain size is less than the standard accepted. Using Solid Works simulation and FEM a model of the stem was created and analyzed in terms of strength and rated the distribution of the generated stress. The finite-element analysis confirmed that there is the highest stress concentration in the middle of the stem