Influence of the Structure of Iron-Titanium Thermal Sprayed Coatings on their Wear Resistance

Abstract

The paper studies the structure, phase composition and properties of thermal sprayed coatings made of Ti4Al titanium alloy and “Ti4Al + AISI420” pseudoalloy obtained by hypersonic metallization. It is shown that the deposited coatings include in the phase composition a large amount of titanium nitride TiN (up to 70 vol.%), which is formed during the metallization process. At the same time, an increase in propane pressure during metallization from 0.3 to 0.4 MPa leads to a slight decrease in the titanium nitride content in the sprayed coating. It is associated with an increase in the flight velocity of molten titanium droplets in an atmosphere of ionized gases and, accordingly, a decrease in the time of their interaction with ionized air nitrogen atoms. The porosity of the sprayed coatings made of titanium alloy Ti4Al is 30–35 vol.%, and their hardness and microhardness are 500–650 HV 1 and 1,300–1,600 HV 0.1, respectively. Coatings made of “Ti4Al + AISI420” pseudoalloy have a reduced porosity of 10–15 vol.%, and their hardness and microhardness are 500–600 HV 1 and 900–1,300 HV 0.1, respectively. It is shown that coatings made of Ti4Al alloy and “Ti4Al + AISI420” pseudoalloy are characterized by increased wear resistance under friction without lubricant. In particular, the intensity of mass wear of coatings Iq made of Ti4Al titanium alloy, obtained at propane pressures of 0.3 and 0.4 MPa, is 2.5–2.6×10–3 mg/m, and Iq for coatings made of “Ti4Al + AISI420” pseudoalloy is 1.0–1.1×10–3 mg/m. The reduced values of mass wear intensities of coatings made of “Ti4Al + AISI420” pseudoalloy are associated with the presence of TiN in them and relatively low porosity.

Keywords

• hypersonic metallization
• titanium alloy
• titanium nitride
• porosity
• microhardness
• wear resistance