Influence Of Lubricating Additives On Friction Properties Of Nickel-based Superalloys

Nickel-based superalloys are widely used in aerospace and other fields because of their excellent high-temperature properties.At the same time,nickel-based superalloys are also recognized as difficult-to-machine metals.High cutting force,high temperature in the cutting area,serious tool wear,and poor surface quality are common problems in the machining of nickel-based superalloys.The use of suitable cutting fluids can effectively improve the machining conditions of nickel-based superalloys.At present,the research on nickel-based superalloys often focuses on tool materials,processing parameters,new cooling and lubrication methods,etc.The research on the surface lubrication law and action mechanism of nickel-based superalloys with commonly used extreme pressure antiwear agents is still very weak.This paper takes nickel-based superalloy/ cemented carbide friction pair as the research object,compares the friction coefficient and wear volume through friction and wear experiments,and analyzes the surface after the experiment through SEM,EDS and XPS,finally explores lubricating effect and film-forming mechanism of common phosphorus and sulfur extreme pressure agents and the polymer synthetic ester on nickel-based superalloy surface.Among the sulfur-containing extreme pressure agents,sulfurized fatty acid ester has the best performance.It has a long carbon chain molecular structure and contains a certain amount of active sulfur,so that it can quickly form a boundary film composed of a physical adsorption film and a chemical adsorption film with the metal surface.In the extreme pressure environment,the increase of temperature and the increase of load will promote the formation of films of S-containing compounds through chemical reactions with Ni and Fe on the metal surface,which play the role of reducing friction and anti-wear.The three phosphate esters have different effects in response to different working conditions: the phosphite ester has better lubricating effect under light load conditions,and the ammonium salt phosphate ester has better lubricating effect and stability under extreme pressure test conditions.After the experiment,the EDS elemental analysis results in the wear scar show that there is no P element in the wear scar,indicating that the three phosphate esters mainly lubricate the nickel-based superalloy through physical adsorption.In addition,a water-soluble polymer synthetic grease(3955)with excellent lubricating properties was also studied.It forms a physical adsorption film on the metal surface through intermolecular van der Waals forces。Moreover,it can play a role at a low concentration(2%).The friction coefficient of the 2% concentration aqueous solution is already smaller than that of the original solution.