Surface contamination from the use of metal powders at two additive manufacturing facilities

Abstract

Additive manufacturing (AM) of metal powders is a relatively new technology, especially in South Africa, therefore little information exists on the potential health hazards involved. Maraging steel, stainless steel, and titanium alloy powders are used in AM process, including the process categories of powder bed fusion (PBF) and directed energy deposition (DED). As such, these powders may contaminate workplace surfaces and contribute to overall inhalation, dermal, and ingestion exposure. Exposure to metal powders such as nickel, chromium, and cobalt, which are steel component metals, can lead to dermal or respiratory sensitisation. Aims and objectives: To determine surface contamination caused by use of maraging steel, stainless steel, and titanium-6aluminium-4vanadium (Ti-6Al-4V) powders during PBF and DED at two AM facilities using a wipe sampling method. Methods: Sampling took place at two AM facilities where maraging steel, stainless steel, and/or Ti-6Al-4V powders were used in PBF and/or DED. Surface wipe sampling was carried out in printing and non-printing areas using Ghostwipes™. Printing activities were divided into three printing phases (pre-processing, processing, and post-processing) and, where possible, samples were collected before and after activities in each of the phases. Even surfaces were wiped three times consecutively following an s-shaped pattern and using a 10 x 10 cm template. Uneven or irregular surfaces were also wiped three times consecutively and the area sampled was measured and used to adjust the results. The surface samples as well as the collected field and media blanks were subjected to inductively coupled argon plasma atomic emission spectroscopy (ICPAES) analysis. Results: Detectable concentrations of aluminium (below detection limit [BDL]-42.422 μg/cm2), calcium (BDL-22.553 μg/cm2), cadmium (BDL-0.051 μg/cm2), cobalt (BDL-66.741 μg/cm2), chromium (BDL-132.727 μg/cm2), copper (BDL-3.84 μg/cm2), iron (BDL-1072.28 μg/cm2), lead (BDL-0.311 μg/cm2), magnesium (BDL-0.351 μg/cm2), manganese (BDL-3.625g/cm2), molybdenum (BDL-22.943 μg/cm2), nickel (BDL-77.539 μg/cm2), tin (BDL-0.217 μg/cm2), titanium (BDL-8.0 μg/cm2), vanadium (BDL-0.538 μg/cm2), and zinc (BDL-1.175 μg/cm2) were found to be present on surfaces in both printing and non-printing areas at both of the AM facilities. Contamination occurred prior to as well as during the different printing phases. When comparing total metal concentrations, significant differences (p ≤ 0.05) were found between the concentrations of contaminants on certain surfaces prior to specific printing phases and the concentrations of contaminants after those printing phases. Cross-contamination was found to occur between AM printing rooms and within AM printing rooms where more than one type of metal powder was used in the printing rooms. Significantly higher metal powder concentrations were found on surfaces in the printing rooms compared to that of surfaces in non-printing rooms. Conclusions: DED with stainless steel powder, and PBF with maraging steel powder and Ti-6Al-4V powder caused detectable levels of metal powder contaminants to be present on printing room surfaces and non-printing room surfaces at both AM facilities. Cross-contamination as a result of airborne and/or contact transfer was found to have occurred from previous print builds with different metal powders in the same room. Contaminated surfaces presented as potential secondary sources of worker exposure through inhalation, dermal contact, and ingestion. Some of the metals that were found to be present on AM surfaces are capable of eliciting toxic responses in humans, including hypersensitivity reactions and cancer, and potential surface contaminationrelated exposure may contribute to the development of the adverse health effects associated with these metals. While surface contamination occurred as a result of the AM activities, poor housekeeping contributed to the extent of surface contamination. The concentrations of metal powders found to be present on surfaces at the AM facilities is comparable to that found in other industries including the cemented tungsten carbide industry.