Surface Topography Analysis of BK7 with Different Roughness Nozzles Using an Abrasive Water Jet

Area of Science:

• Materials Science
• Manufacturing Engineering
• Surface Metrology

Background:

• Abrasive water jet (AWJ) machining is a key process for shaping and finishing materials.
• Optimizing AWJ kinematic parameters is crucial for achieving desired surface quality and wear resistance.
• BK7 glass is a common optical material susceptible to surface damage during machining.

Purpose of the Study:

• To investigate the influence of AWJ kinematic parameters on BK7 surface quality.
• To evaluate the effectiveness of titanium alloy nozzle coatings for enhanced wear resistance.
• To determine optimal machining conditions for achieving a super-smooth BK7 surface.

Main Methods:

• AWJ machining experiments were conducted on BK7 glass.
• Kinematic parameters varied: traverse speed, water pressure, abrasive flow rate, and standoff distance.
• Surface topography measurements, including average roughness (Ra) and maximum height (PV), were used for analysis.
• Analysis of variance (ANOVA) was employed to assess parameter significance.

Main Results:

• A nozzle coated with 100 nm titanium alloy exhibited superior wear resistance compared to an uncoated nozzle.
• Higher water pressure (3 MPa) and a traverse speed of 7.8 mm/min with 2% titanium alloy in the nozzle resulted in a smoother BK7 surface (Ra 15.734 nm).
• Higher water pressure improved material removal and cleaning, leading to better surface quality.

Conclusions:

• Titanium alloy nozzle coatings enhance BK7 surface hardness and smoothness.
• Optimized AWJ parameters, particularly higher water pressure and specific traverse speeds, are critical for superior surface finish.
• AWJ machining with appropriate parameters and nozzle coatings offers a viable method for producing high-quality BK7 optical surfaces.