Additive manufacturing of metallic components – Process, structure and properties

Unlike conventional materials removal methods, additive manufacturing (AM) is based on a novel materials incremental manufacturing philosophy. Additive manufacturing implies layer by layer shaping and consolidation of powder feedstock to arbitrary configurations, normally using a computer controlled laser. The current development focus of AM is to produce complex shaped functional metallic components, including metals, alloys and metal matrix composites (MMCs), to meet demanding requirements from aerospace, defence, automotive and biomedical industries. Laser sintering (LS), laser melting (LM) and laser metal deposition (LMD) are presently regarded as the three most versatile AM processes. Laser based AM processes generally have a complex non-equilibrium physical and chemical metallurgical nature, which is material and process dependent. The influence of material characteristics and processing conditions on metallurgical mechanisms and resultant microstructural and mechanical properties of AM proc...

Laser additive manufacturing of metallic components: materials, processes and mechanisms

A study of the microstructural evolution during selective laser melting of Ti–6Al–4V

Topological design and additive manufacturing of porous metals for bone scaffolds and orthopaedic implants: A review.

https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1037&context=mepubs

Additive manufacturing of Ti6Al4V alloy: A review

Structural, mechanical and in vitro characterization of individually structured Ti-6Al-4V produced by direct laser forming.

This prospective, randomised clinical trial compared pain, comfort, exudate management, wound healing and safety with Hydrofiber dressing with ionic silver (Hydrofiber Ag dressing) and with povidone-iodine gauze for the treatment of open surgical and traumatic wounds. Patients were treated with Hydrofiber Ag dressing or povidone-iodine gauze for up to 2 weeks. Pain severity was measured with a 10-cm visual analogue scale (VAS). Other parameters were assessed clinically with various scales. Pain VAS scores decreased during dressing removal in both groups, and decreased while the dressing was in place in the Hydrofiber Ag dressing group (n = 35) but not in the povidone-iodine gauze group (n = 32). Pain VAS scores were similar between treatment groups. At final evaluation, Hydrofiber Ag dressing was significantly better than povidone-iodine gauze for overall ability to manage pain (P < 0.001), overall comfort (P < or = 0.001), wound trauma on dressing removal (P = 0.001), exudate handling (P < 0.001) and ease of use (P < or = 0.001). Rates of complete healing at study completion were 23% for Hydrofiber Ag dressing and 9% for povidone-iodine gauze (P = ns). No adverse events were reported with Hydrofiber Ag dressing; one subject discontinued povidone-iodine gauze due to adverse skin reaction. Hydrofiber Ag dressing supported wound healing and reduced overall pain compared with povidone-iodine gauze in the treatment of open surgical wounds requiring an antimicrobial dressing.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1742-481X.2006.00276.x

Randomised clinical trial of Hydrofiber dressing with silver versus povidone–iodine gauze in the management of open surgical and traumatic wounds

There is a great need to establish reproducible methods for evaluative studies of wound treatment and wound healing. Validation of the healing process through optical techniques, as well as histologic and immunohistochemical methodologies, have been improved and to some extent have become well-established assays. Data relating to biomechanical properties, e.g., evaluation of the tensile strength of scar tissue that forms in experimental wound treatment strategies, are less widely available. We chose the domestic pig as an animal model in which to examine epidermal wound healing. We implanted specially made chambers that served to isolate the wounds and prevent epidermal migration from the edges. We performed histologic and immunohistochemical analyses as well as evaluation of biomechanical qualities of scar tissue using laser tensiometry. Pig skin is well suited for wound healing studies, and wound creation, implantation of the chambers, and the regular changing of dressings could all be carried out in the operating theater. In addition to established macroscopic evaluation and microscopic documentation, the need for objective biomechanical assessment of scar tissue by measuring tensile strength has been met using laser tensiometry. By optimizing methods for measuring tensile strength, it is possible to evaluate the biomechanical quality of scar tissue formed following different courses of wound treatment, as well as histologic assessment. (WOUND REP REG 2003;11:150–157)

Standardized qualitative evaluation of scar tissue properties in an animal wound healing model

The effect of surface modification of a porous TiO2/perlite composite on the ingrowth of bone tissue in vivo.

Scientific approach is the utilization of the new
generative manufacturing process termed Selective Laser Melting
(SLM) for the creation of biocompatible three-dimensional (3-D)
bone substitutes made of the titanium alloy TiAl6V4. The SLM
technique enables direct transfer of virtual 3-D structures into
solid metal materials with full serial characteristics and
typically great freedom of geometric design. Individual 3-D CAD data which are derived from computed
tomography models of anatomic structures are subdivided into
layers of defined thickness. The actual part is generated by a
repeating process of applying TiAl6V4 powder in layers of
0.003–0.1 mm on the process chamber platform transferring the
area and contour information of each layer into the material
using a laser beam. The physical process is a complete remelting
of the powder with a metallurgical bonding between the layers
yielding densities of approximately 100%. This operation is
repeated step by step until the generation of the 3-D part is
completed. We cultured human primary osteoblast-like cells on
different surfaces of SLMmanufactured TiAl6V4 parts to prove
osteoblast compatibility. Proliferation, vitality, and alkaline
phosphatase (AP) activity of osteoblast cultures are
presented. It has become possible to produce complex 3-D geometries
with different surface properties within few hours.
Compatibility of the tested TiAl6V4 material with human
osteoblasts is demonstrated. The cultured cells attach and
proliferate on SLM substrates and show AP activity. The presented results demonstrate the potential offered by
the SLM process. On the basis of scanned information, the
generation of complex anatomic structures is realizable. The
presented promising advantages make this procedure interesting
for the production of individual implants or bone
substitutes.

Dirk A. Hollander

Papers

Structural, mechanical and in vitro characterization of individually structured Ti-6Al-4V produced by direct laser forming.

Randomised clinical trial of Hydrofiber dressing with silver versus povidone–iodine gauze in the management of open surgical and traumatic wounds

Standardized qualitative evaluation of scar tissue properties in an animal wound healing model

The effect of surface modification of a porous TiO2/perlite composite on the ingrowth of bone tissue in vivo.

Development of Individual Three-Dimensional Bone Substitutes Using “Selective Laser Melting”