A comparison of laser deposition of commercially pure titanium using gas atomized or Ti sponge powders

Abstract

In this work, results obtained on the laser metal deposition of commercially pure titanium (CP Ti) using two different Ti powders are presented and compared. Nominal composition of both materials complies with CP Ti standards but they are produced by two different manufacturing routes: gas atomization and sponge fines from the Kroll process. They differ in morphology (spherical and irregular, respectively) and the amount of residual and interstitial elements in their composition. The purpose of the study is to analyze the possible implications of the use of one or the other type of powder on the laser processing characteristics and the final properties of the deposited material. Ti layers were deposited over a conventional CP Ti plate. Under metallographic inspection, both materials showed similar phase composition and microstructure patterns. Measurable differences were though encountered regarding microhardness and corrosion resistance. Hardness of deposited CP Ti from sponge powders is higher than the obtained from gas atomized powders. Its corrosion behavior, evaluated with electrochemical tests in a 3.5 wt% NaCl solution, is poorer but nevertheless comparable to the one displayed by a conventionally manufactured CP Ti plate. Based on the results obtained, the use of sponge powders for laser manufacturing of commercially pure titanium appear as a potential and interesting alternative to the customary spherical atomized powders, particularly when cost savings are of main concern.