Try This:
chart1.ChartAreas[0].AxisX.MajorGrid.LineWidth = 0;
chart1.ChartAreas[0].AxisX.MinorGrid.LineWidth = 0;
chart1.ChartAreas[0].AxisY.MajorGrid.LineWidth = 0;
chart1.ChartAreas[0].AxisY.MinorGrid.LineWidth = 0;
To disable X-Axis
Labels from the Chart :
chart1.ChartAreas[0].AxisX.LabelStyle.Enabled = false;