Research On Wear Resistant Material And Laser Strengthening Technology Of High Parameter Ball Valve In Coal Chemical Industry

High parameter wear resistant ball valve is an important component for modern coal chemical industry under high pressure and high temperature,and its characteristic of high hardness sealing surface will effect directly the valve operation lifetime.Due to the exist discrepancy between the hardness and process implementation,the higher the hardness of wear resistant surface is,the more difficult the process implementation is.So based on the previous engineering applications,the material with high hardness was developed,adopting laser process to deposit the ball surface,this could bring hardness of wear-resistant deposit layer to 62 HRC and higher.This technologycould increase the service period of coal chemical industry equipment,as well as work efficiency and reduce cost.A new compound powder material was developed in this paper.Ni60 was selected as the main composition,45%WC and other element was added to achieve the solution strengthening,the second-phase strengthening,and grain boundary strengthening.According to the WC particle hard phase crystalline principle,Siand Y2O3 nanometer particle was added properly as the strengthening element.And combined with phase calculation principle,the average electronic density of the powder formula was calculated to adjust the powder element slightly,thus the harmful phases could be controlled in the alloy design phase.The powder was deposited through laser process,and the deposit layer wasstudied by microscopic structure analysis,mechanical property/hardness and combining strengthening test.The best powder formula was confirmed and named Ni60+45%WC compound powder.The microscopic structure analysis of laser deposit layer indicated that deposit metal and base material macroscopic forms reflected the bondingcondition,the interface area was good metallurgy bonding with no obvious gas porosity and cracking.Multi-layer and multiple alloy structure was mainly distributed in diffusion with cell crystal and hard phase.According to EDS and XRD analysis,the metal base Cr4Ni15 W solid solution and WC particle with hardening characteristic distributed in diffusion.The area fraction of the WC particle in the deposit layer structure was 43%.Abundant of diffusion-distributed spheroidal WC particle ensure the strength and hardness of deposit structure.The micro-hardness test indicates that the average micro-hardness is 63-64 HRC for Ni60+45%WC compound powder with multi deposit layer under room temperature,which can meet the special service in coal chemical industry.And for the equipmentwith particle medium,the long period time service requirement could be met.The related process was adjusted based on the deposit sample,the 6” ball surface was deposited with big area and multi layers,the thickness could reach to 1-1.5mm and higher.The deposit surface wasgrinded,the surface quality was qualified through liquid penetrant test.High pressure closure test and high temperature thermal test were performed after assembly,and results showed that the deposit layer was in good condition and have achieved the good closure function.