Investigation Into High Hardness Fe-based Alloy Coatings Reinforced With TiC_p By Laser Deposition

Ni-based,Co-based and Fe-based alloys are widely used in laser deposition of high-performance coatings.At present,researchers mostly use ceramic phase reinforced Co-based or Ni-based alloy powder to prepare high temperature wear-resistant coatings on various workpieces.However,the cost of Co-based and Nibased alloy powder is relatively high,and most of the strengthened workpiece materials belong to iron-based alloy,which is quite different from the composition of coating.Therefore,the prepared Co based/Ni based alloy coating has high dilution ratio and is prone to porosity,cracks and other defects.Due to the poor high-temperature wear resistance of Fe-based alloys,there are few researches on Fe /TiC high-temperature wear-resistant coatings at present,and we expect to improve the high-temperature properties by changing the composition of Fe-based alloys.In the present study,various kinds of Fe/TiC and Co/TiC wear-resistant coatings were produced on the surface of 45 steel by diode laser deposition technology.Surface and cross-section topography,microstructures,interfacial characteristic and wear properties of coatings at different temperatures were investigated by means of optical microscopy(OM),scanning electronic microscopy(SEM),X-ray diffraction(XRD),micro vickers hardness meter and high-temperature ring-on-block wear tester.Three Fe-based alloys(350,366 H and 345 H respectively)were used as bonding phases and compared with two Co-based alloys(530 and 550 respectively).Deposition layers with different content of angular particles TiCp(204 hereinafter referred to as 204)were prepared on 45 steel surface.It is found that with the increase of TiC content,the crack sensitivity of the deposited layer increases.Moreover,the crack resistance of Fe-based alloy is prior to that of Co-based alloy,according to the results of 345H/204 composite coatings exhibiting the best crack resistance while550/204 showing the worst.Besides,the matrix phases of 350,345 H,530 and 550 deposits are dendrite.And with the rise of TiC content,the structure of the deposit is refined gradually,leading to the existence of reticular cellular crystals in 366 H deposit.When the TiC content in the deposited layer reaches 20%,flower shaped or granular secondary carbides with smaller size are precipitated in the matrix phase.In addition,the precipitated secondary carbides are approved to be still TiC by the XRD analysis.The hardness of the composite coatings are significantly higher than that of the pure Fe-based or Co-based coatings.At room temperature,the wear resistance of the composite coatings is positively related to its hardness.Under the condition of the same TiC content at 600℃,the wear resistance of Co-based alloy deposits is better than that of Fe-based alloy deposits.Besides,the wear resistance of 345H/204 deposits increases with the increasing of content of 204.At room temperature,various deposits all display the wear mechanism of abrasive wear except 530/20%204appearing adhesive and abrasive wear.At 600℃,the wear forms of 350/20%204 and366H/20%204 composite coatings are oxidative and adhesive wear,while that of530/20%204 and 550/20%204 being oxidative,adhesive and abrasive one.Oxidative,adhesive and abrasive wear dominate the wear process of 345H/20%204 while oxidative and abrasive wear governing that of 345H/40%204 and 345H/60%204.Furthermore,345H/60%204 deposit presents the best wear resistance at room and high temperature.