A study on tribological behavior of double-glow plasma surface alloying W-Mo coating on gear steel

• The W-Mo coating was formed on the gear steel by double-glow plasma surface alloying technique.
• The hardness (H), elastic modulus (E) and adhesion strength of coating were discussed.
• The W-Mo coating produced by DG Technique has contributed to better tribological properties both at room and high temperature.

In the present study, a dense W-Mo coating was formed onto the gear steel by using double-glow plasma surface alloying technique. The nanoindentation test was used to measure the hardness and elasticity modulus of the coating. The scratch test was applied to evaluate the critical load for coating delamination, which measured the adhesion strength of the coating. The tribological behavior of the W-Mo coating was estimated using a pin-on-disc tribometer by rubbing against the Si3N4 ceramic ball. Results showed that the W-Mo coating was well diffusely bonded to the substrate. In terms of the H/E and H3/E2 ratios, the coated sample was nearly two times greater than that of the uncoated sample. The specific wear rates of the W-Mo coating at room and high temperature were 8.1 × 10− 5 mm3N− 1 m− 1 and 11.2 × 10− 5 mm3N− 1 m− 1 respectively, about only 19% of that of the uncoated sample. The excellent wear resistance of the W-Mo coating may be due to its high resistance to plastic deformation and good load bearing capacity.