Nuclear Zr-4 Lubrication Mechanism Of Hot Extrusion And Parameter Optimization

Nuclear-grade zirconium alloy is widely used in water-cooled nuclear reactor core structural materials,and most of these structural materials are processed by the hot extrusion process.However,zirconium alloys are easily contaminated by oxygen,nitrogen and hydrogen in high-temperature environments,and it is easy to stick to the mold during hot processing.Therefore,it is very important to choose the lubrication method of nuclear-grade zirconium alloy.This paper takes commercial bonded solid lubricating coatings as the object,analyze the composition and lubricating properties of these coatings under different temperature conditionsAt the same time,this paper designs a set of laboratory-specific hot extrusion die to explore the lubricating effect of these coatings in hot extrusion.And combined Deform-3D simulation performance analysis extrusion,provide theoretical guidance extrusion nuclear zirconium alloy such as bonded type solid lubricating coatings applied.This paper takes the commercially available bonded solid lubricant coatings as the research object to determine the composition of the coatings.,and the lubricating performance of the coatings at different temperatures is analyzed.The results show that the lubricant component?MoS₂?C?still exists in the coatings at 200?-600?,and the starting oxidation temperature of MoS₂ is about 550?.After the coatings were heated to600?,the coatings friction coefficient also increased due to the gradual oxidation and failure of the coatings.The coatings have failed at 700?,and MoS₂ and graphite have been completely oxidized to become MoO₃ and molybdate.According to the high-temperature friction and wear test,the coatings can still maintain excellent anti-wear performance at 400?and 600?,and the effective friction coefficient is below 0.1.When the coatings were kept at 600?for 60 minutes,Mo⁴⁺was oxidized to Mo^6+,which caused the formation of bumps,cracks and bubbles on the surface of the coatings,and the lubricating performance of the coatings were greatly reduced.It can be known from the research on coatings structure and lubrication performance,the main factor affecting the lubricating performance of the bonded solid lubricating coatings are the oxidation problem of the sample for too long ina high-temperature atmospheric environment.It is not the tribochemical problem of the coatings under high temperature and strong load during friction and wear.This paper takes the hot extrusion parameters of industrial grade nuclear zirconium alloy as a reference to design a set of hot extrusion die.Through calculation,the cooperation between the molds and the mold strength are ensured,and the designed hot extrusion mold can be smoothly applied to the laboratory hydraulic press.By performing Deform-3D simulation on this hot extrusion die,it is preliminarily determined that when the heating temperature is 680?-740?,the extrusion speed is 3-5mm/s,and the friction coefficient is 0.35,the performance of the extrusion is better in all aspects.Then,hot extrusion experiments were carried out on the samples coated with these commercial bonded solid lubricating coatings.When the extrusion temperature is 680?,the holding time is 10-20min,and the extrusion speed is 3-5mm/s,the extruded parts have excellent performance.The extrusion length and shape are good,and the results are similar to the Deform-3D simulation results.