The　utilization　of　high-density　polyethylene　(HDPE)　pipes　is　prevalent　in　water　transportation　due　to　their　exceptional　durability,　resistance　to　corrosion,　and　ease　of　installation.　Traditionally,　butt　fusion　welding　has　been　employed　to　connect　HDPE　pipes.　In　this　study,　scanning　electron　microscopy　(SEM)　was　utilized　to　examine　the　microstructure　of　butt　fusion　welded　joints　of　HDPE　pipes,　while　the　stepped　isostress　method　(SSM)　was　employed　to　investigate　their　creep　behavior　at　100　degrees　C　in　ambient　air.　SEM　results　revealed　a　significant　presence　of　craze　or　lamellae　in　the　base　material,　whereas　minimal　occurrences　of　craze　or　lamellae　were　observed　in　the　melt　zone.　The　results　obtained　from　the　SSM　indicated　that　the　creep　life　of　butt　fusion　welded　joints　of　HDPE　pipes　was　not　adversely　affected　by　the　welding　bead,　and　their　creep　life　was　no　less　than　that　of　the　base　material　when　ductile　creep　failure　occurred.